View source for Climate change and infectious diseases

{{short description|Overview of the relationship between climate change and infectious diseases}}
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{{Use dmy dates|date=March 2023|cs1-dates=ls}}<!-- see talk page for rationale -->[[File:Aedes aegypti CDC9253.tif|thumb|Climate change is altering the geographic range and seasonality of some insects that can carry diseases, for example ''[[Aedes aegypti]]'', the mosquito that is the [[Disease vector|vector]] for [[dengue]] transmission.]]
Global [[climate change]] has increased the occurrence of some [[infectious diseases]].<ref>{{cite journal |last1=Van de Vuurst |first1=Paige |last2=Escobar |first2=Luis E. |title=Climate change and infectious disease: a review of evidence and research trends |journal=Infectious Diseases of Poverty |date=2023 |volume=12 |issue=1 |pages=51 |doi=10.1186/s40249-023-01102-2 |doi-access=free|hdl=10919/115131 |hdl-access=free }}</ref> Infectious diseases whose transmission is impacted by climate change include, for example, [[vector-borne disease]]s like [[dengue fever]], [[malaria]], [[tick-borne disease]]s, [[leishmaniasis]], [[zika fever]], [[chikungunya]] and [[Ebola]]. One mechanism contributing to increased disease transmission is that climate change is altering the geographic range and seasonality of the insects (or [[disease vector]]s) that can carry the diseases. Scientists stated a clear observation in 2022: "The occurrence of climate-related [[Foodborne illness|food-borne]] and [[waterborne diseases]] has increased (very high confidence)."<ref name=":1">IPCC, 2022: [https://www.ipcc.ch/report/ar6/wg2/downloads/report/IPCC_AR6_WGII_SummaryForPolicymakers.pdf Summary for Policymakers] [H.-O. Pörtner, D.C. Roberts, E.S. Poloczanska, K. Mintenbeck, M. Tignor, A. Alegría, M. Craig, S. Langsdorf, S. Löschke, V. Möller, A. Okem (eds.)]. In: [https://www.ipcc.ch/report/ar6/wg2/ Climate Change 2022: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change] [H.-O. Pörtner, D.C. Roberts, M. Tignor, E.S. Poloczanska, K. Mintenbeck, A. Alegría, M. Craig, S. Langsdorf, S. Löschke, V. Möller, A. Okem, B. Rama (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA, pp. 3–33, doi:10.1017/9781009325844.001.</ref>{{rp|11}}

Infectious diseases that are sensitive to climate can be grouped into: vector-borne diseases (transmitted via [[mosquito]]s, [[tick]]s etc.), waterborne diseases (transmitted via viruses or bacteria through water), and food-borne diseases.(spread through pathogens via food)<ref name=":16">Cissé, G., R. McLeman, H. Adams, P. Aldunce, K. Bowen, D. Campbell-Lendrum, S. Clayton, K.L. Ebi, J. Hess, C. Huang, Q. Liu, G. McGregor, J. Semenza, and M.C. Tirado, 2022: [https://www.ipcc.ch/report/ar6/wg2/downloads/report/IPCC_AR6_WGII_Chapter07.pdf Chapter 7: Health, Wellbeing, and the Changing Structure of Communities]. In: [https://www.ipcc.ch/report/ar6/wg2/ Climate Change 2022: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change] [H.-O. Pörtner, D.C. Roberts, M. Tignor, E.S. Poloczanska, K. Mintenbeck, A. Alegría, M. Craig, S. Langsdorf, S. Löschke, V. Möller, A. Okem, B. Rama (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA, pp. 1041–1170, doi:10.1017/9781009325844.009.</ref>{{rp|1107}} Climate change affects the distribution of these diseases due to the expanding geographic range and seasonality of these diseases and their vectors.<ref name="Romanello2021">{{cite journal |last1=Romanello |first1=Marina |last2=McGushin |first2=Alice |last3=Di Napoli |first3=Claudia |last4=Drummond |first4=Paul |last5=Hughes |first5=Nick |last6=Jamart |first6=Louis |last7=Kennard |first7=Harry |last8=Lampard |first8=Pete |last9=Solano Rodriguez |first9=Baltazar |last10=Arnell |first10=Nigel |last11=Ayeb-Karlsson |first11=Sonja |last12=Belesova |first12=Kristine |last13=Cai |first13=Wenjia |last14=Campbell-Lendrum |first14=Diarmid |last15=Capstick |first15=Stuart |display-authors=40 |date=October 2021 |title=The 2021 report of the Lancet Countdown on health and climate change: code red for a healthy future |url=http://sro.sussex.ac.uk/id/eprint/102413/1/2021%20Report%20of%20the%20Lancet%20Countdown%20revised%20_no%20refs%20ES_clean.pdf |journal=The Lancet |volume=398 |issue=10311 |pages=1619–1662 |doi=10.1016/S0140-6736(21)01787-6 |pmid=34687662 |s2cid=239046862 |hdl-access=free |last16=Chambers |first16=Jonathan |last17=Chu |first17=Lingzhi |last18=Ciampi |first18=Luisa |last19=Dalin |first19=Carole |last20=Dasandi |first20=Niheer |last21=Dasgupta |first21=Shouro |last22=Davies |first22=Michael |last23=Dominguez-Salas |first23=Paula |last24=Dubrow |first24=Robert |last25=Ebi |first25=Kristie L |last26=Eckelman |first26=Matthew |last27=Ekins |first27=Paul |last28=Escobar |first28=Luis E |last29=Georgeson |first29=Lucien |last30=Grace |first30=Delia |last31=Graham |first31=Hilary |last32=Gunther |first32=Samuel H |last33=Hartinger |first33=Stella |last34=He |first34=Kehan |last35=Heaviside |first35=Clare |last36=Hess |first36=Jeremy |last37=Hsu |first37=Shih-Che |last38=Jankin |first38=Slava |last39=Jimenez |first39=Marcia P |last40=Kelman |first40=Ilan |last41=Kiesewetter |first41=Gregor |last42=Kinney |first42=Patrick L |last43=Kjellstrom |first43=Tord |last44=Kniveton |first44=Dominic |last45=Lee |first45=Jason K W |last46=Lemke |first46=Bruno |last47=Liu |first47=Yang |last48=Liu |first48=Zhao |last49=Lott |first49=Melissa |last50=Lowe |first50=Rachel |last51=Martinez-Urtaza |first51=Jaime |last52=Maslin |first52=Mark |last53=McAllister |first53=Lucy |last54=McMichael |first54=Celia |last55=Mi |first55=Zhifu |last56=Milner |first56=James |last57=Minor |first57=Kelton |last58=Mohajeri |first58=Nahid |last59=Moradi-Lakeh |first59=Maziar |last60=Morrissey |first60=Karyn |last61=Munzert |first61=Simon |last62=Murray |first62=Kris A |last63=Neville |first63=Tara |last64=Nilsson |first64=Maria |last65=Obradovich |first65=Nick |last66=Sewe |first66=Maquins Odhiambo |last67=Oreszczyn |first67=Tadj |last68=Otto |first68=Matthias |last69=Owfi |first69=Fereidoon |last70=Pearman |first70=Olivia |last71=Pencheon |first71=David |last72=Rabbaniha |first72=Mahnaz |last73=Robinson |first73=Elizabeth |last74=Rocklöv |first74=Joacim |last75=Salas |first75=Renee N |last76=Semenza |first76=Jan C |last77=Sherman |first77=Jodi |last78=Shi |first78=Liuhua |last79=Springmann |first79=Marco |last80=Tabatabaei |first80=Meisam |last81=Taylor |first81=Jonathon |last82=Trinanes |first82=Joaquin |last83=Shumake-Guillemot |first83=Joy |last84=Vu |first84=Bryan |last85=Wagner |first85=Fabian |last86=Wilkinson |first86=Paul |last87=Winning |first87=Matthew |last88=Yglesias |first88=Marisol |last89=Zhang |first89=Shihui |last90=Gong |first90=Peng |last91=Montgomery |first91=Hugh |last92=Costello |first92=Anthony |last93=Hamilton |first93=Ian |hdl=10278/3746207}}</ref>[[Waterborne diseases|{{rp|9}}]] Like other ways climate change affects [[Effects of climate change on human health|human health]], climate change exacerbates existing inequalities and challenges in managing infectious disease. 

Mosquito-borne diseases that are sensitive to climate include [[malaria]], [[lymphatic filariasis]], [[Rift Valley fever]], [[yellow fever]], dengue fever, [[Zika virus]], and [[chikungunya]].<ref name="Mosquitoes-Borne Disease">{{cite journal |last=Reiter |first=Paul |year=2001 |title=Climate Change and Mosquito-Borne Disease |url=http://ehpnet1.niehs.nih.gov/docs/2001/suppl-1/141-161reiter/abstract.html |journal=Environmental Health Perspectives |volume=109 |issue=1 |pages=141–161 |doi=10.1289/ehp.01109s1141 |pmc=1240549 |pmid=11250812 |archive-url=https://web.archive.org/web/20110824222504/http://ehpnet1.niehs.nih.gov/docs/2001/suppl-1/141-161reiter/abstract.html |archive-date=24 August 2011}}</ref><ref name="elephantiasis">{{cite journal |last=Hunter |first=P.R. |year=2003 |title=Climate change and waterborne and vector-borne disease |journal=[[Journal of Applied Microbiology]] |volume=94 |pages=37S–46S |doi=10.1046/j.1365-2672.94.s1.5.x |pmid=12675935 |s2cid=9338260 |doi-access=free}}</ref><ref name="Climate change & health">{{cite journal |last1=McMichael |first1=A.J. |last2=Woodruff |first2=R.E. |last3=Hales |first3=S. |date=11 March 2006 |title=Climate change and human health: present and future risks |journal=[[The Lancet]] |volume=367 |issue=9513 |pages=859–869 |doi=10.1016/s0140-6736(06)68079-3 |pmid=16530580 |s2cid=11220212}}</ref> Scientists found in 2022 that rising temperatures are increasing the areas where dengue fever, malaria and other mosquito-carried diseases are able to spread.<ref name=":16" />{{rp|1062}} Warmer temperatures are also advancing to higher elevations, allowing mosquitoes to survive in places that were previously in hospitable to them.<ref name=":16" />{{rp|1045}} This risks malaria returning to areas where it was previously eradicated.<ref name="The Mosquito's Bite">{{cite book |last1=Epstein |first1=Paul R. |url=https://archive.org/details/unset0000unse_c1j4/page/29 |title=Changing Planet, Changing Health: How the Climate Crisis Threatens Our Health and what We Can Do about it |last2=Ferber |first2=Dan |publisher=University of California Press |year=2011 |isbn=978-0-520-26909-5 |pages=[https://archive.org/details/unset0000unse_c1j4/page/29 29–61] |chapter=The Mosquito's Bite |chapter-url=https://books.google.com/books?id=nnOkFhXo8rEC&pg=PA29}}</ref>

Ticks are changing their geographic range because of rising temperatures, and this puts new populations at risk. Ticks can spread [[lyme disease]] and [[tick-borne encephalitis]]. It is expected that climate change will increase the incidence of these diseases in the Northern Hemisphere.<ref name=":16" />{{rp|1094}} For example, a review of the literature found that "In the USA, a 2°C warming could increase the number of lyme disease cases by over 20% over the coming decades and lead to an earlier onset and longer length of the annual Lyme disease season".<ref name=":16" />{{rp|1094}}

Waterborne diseases are transmitted through water. The symptoms of waterborne diseases typically include [[diarrhea]], fever and other flu-like symptoms, neurological disorders, and liver damage.<ref name="(Levy et al., 2018)">{{cite journal |vauthors=Levy K, Smith SM, Carlton EJ |date=June 2018 |title=Climate Change Impacts on Waterborne Diseases: Moving Toward Designing Interventions |journal=Current Environmental Health Reports |volume=5 |issue=2 |pages=272–282 |doi=10.1007/s40572-018-0199-7 |pmc=6119235 |pmid=29721700}}</ref> Climate changes have a large effect on the distribution of microbial species. These communities are very complex and can be extremely sensitive to external climate stimuli.<ref name="(Walker, 2018)">{{cite journal |vauthors=Walker JT |date=September 2018 |title=The influence of climate change on waterborne disease and Legionella: a review |journal=Perspectives in Public Health |volume=138 |issue=5 |pages=282–286 |doi=10.1177/1757913918791198 |pmid=30156484 |s2cid=52115812}}</ref>  There is a range of waterborne diseases and parasites that will pose greater health risks in the future. This will vary by region. For example, in Africa, [[Cryptosporidium]]'' spp. and ''[[Giardia duodenalis]]'' ([[protozoan parasite]]s) will increase. This is due to increasing temperatures and drought.<ref name=":16" />{{rp|1095}}

Scientist also expect that disease outbreaks caused by [[vibrio]] (in particular the bacterium that causes [[cholera]], called [[vibrio cholerae]]) are increasing in occurrence and intensity.<ref name=":16" />{{rp|1107}} One reason is that the area of coastline with suitable conditions for vibrio bacteria has increased due to changes in [[sea surface temperature]] and sea surface salinity caused by climate change.<ref name="Romanello2021" />[[Waterborne diseases|{{rp|12}}]] These pathogens can cause [[gastroenteritis]], cholera, wound infections, and [[sepsis]]. The increasing occurrence of higher temperature days, heavy rainfall events and flooding due to climate change could lead to an increase in cholera risks.<ref name=":16" />{{rp|1045}}{{TOC level|3}}

== Public health context ==
In 1988, little was known about the [[effects of climate change on human health]].<ref name="WHO Climate Change and Human Health 2003">{{Cite book |url=https://apps.who.int/iris/bitstream/handle/10665/42749/9241590815.pdf |title=Climate change and human health – risks and responses. Summary. |vauthors=WHO, WMO, UNEP |publisher=World Health Organization |year=2003 |isbn=9241590815 |location=Geneva, Switzerland |chapter=International consensus on the science of climate and health: the IPCC Third Assessment Report |type=Summary of other published book |access-date=28 June 2020 |chapter-url=https://www.who.int/globalchange/summary/en/index2.html}}</ref> As of 2023, the evidence has grown significantly and is for example summarised in the [[IPCC Sixth Assessment Report|Sixth Assessment Report]] of the [[Intergovernmental Panel on Climate Change]].<ref name=":16" /> The scientific understanding of potential health risks and observed health impacts caused by climate change is now better understood. One category of health risks is that of [[infectious diseases]]. A study concluded in 2022 that "58% (that is, 218 out of 375) of infectious diseases confronted by humanity worldwide have been at some point aggravated by climatic hazards".<ref>{{cite news |date=8 August 2022 |title=Climate impacts have worsened vast range of human diseases |language=en |work=The Guardian |url=https://www.theguardian.com/environment/2022/aug/08/climate-crisis-study-human-diseases |access-date=15 September 2022}}</ref><ref name="Mora_2022">{{cite journal | vauthors = Mora C, McKenzie T, Gaw IM, Dean JM, von Hammerstein H, Knudson TA, Setter RO, Smith CZ, Webster KM, Patz JA, Franklin EC | display-authors = 6 | title = Over half of known human pathogenic diseases can be aggravated by climate change | journal = Nature Climate Change | volume = 12 | issue = 9 | pages = 869–875 | date = September 2022 | pmid = 35968032 | pmc = 9362357 | doi = 10.1038/s41558-022-01426-1 | bibcode = 2022NatCC..12..869M }}</ref> The [[World Health Organization]] considers climate change as one of the greatest threats to human health.<ref name="Caminade219">{{cite journal | vauthors = Caminade C, McIntyre KM, Jones AE | title = Impact of recent and future climate change on vector-borne diseases | journal = Annals of the New York Academy of Sciences | volume = 1436 | issue = 1 | pages = 157–173 | date = January 2019 | pmid = 30120891 | pmc = 6378404 | doi = 10.1111/nyas.13950 | bibcode = 2019NYASA1436..157C | doi-access = free }} [[File:CC-BY_icon.svg|50x50px]] Text was copied from this source, which is available under a [[creativecommons:by/4.0/|Creative Commons Attribution 4.0 International License]]</ref> 

Infectious diseases have played a significant role in human history, impacting the rise and fall of civilizations and facilitating the conquest of new territories.<ref name="Caminade219" /> During recent decades, there are significant regional changes in [[Disease vector|vector]] and [[pathogen]] distribution reported in temperate, peri‐Arctic, Arctic, and tropical highland regions.

Climate change is one of the factors that causes the spread of human diseases. Other key factors, include the mobility of people, animals, and goods; control measures in place; availability of effective drugs; quality of public health services; human behavior; and political stability and conflicts.<ref name="Caminade219" /> The March 2022 report from the [[Intergovernmental Panel on Climate Change|Intergovernmental Panel on Climate Change (IPCC)]] warned that without swift climate action we will see an escalation of infectious diseases. They will spread to new regions  (may decline in some endemic areas) and surge in areas where they were previously under control. As a result, diseases that have never previously infected humans (Disease X) may 'spill over' from animals<ref name=":0">{{Cite web |date=2023-12-01 |title=What is the link between climate change and infectious disease? {{!}} PreventionWeb |url=https://www.preventionweb.net/news/what-link-between-climate-change-and-infectious-disease |access-date=2024-07-11 |website=www.preventionweb.net |language=en}}</ref> 

Global warming, increased drought and flooding represent a significant threat to public health, likely leading to the escalation of vector, food and water-borne diseases<ref name=":0" /> The effects of climate change on health will impact most populations over the next few decades.<ref name=":2">{{cite journal | vauthors = Costello A, Abbas M, Allen A, Ball S, Bell S, Bellamy R, Friel S, Groce N, Johnson A, Kett M, Lee M, Levy C, Maslin M, McCoy D, McGuire B, Montgomery H, Napier D, Pagel C, Patel J, de Oliveira JA, Redclift N, Rees H, Rogger D, Scott J, Stephenson J, Twigg J, Wolff J, Patterson C | display-authors = 6 | title = Managing the health effects of climate change: Lancet and University College London Institute for Global Health Commission | journal = Lancet | volume = 373 | issue = 9676 | pages = 1693–1733 | date = May 2009 | pmid = 19447250 | doi = 10.1016/S0140-6736(09)60935-1 | s2cid = 205954939 }}</ref> However, Africa, and specifically, the African Highlands, are susceptible to being particularly negatively affected. For example, with regard to malaria, in 2010, 91% of the global burden due to malaria deaths occurred in Africa. Several spatiotemporal models have been studied to assess the potential effect of projected climate scenarios on malaria transmission in Africa. It is expected that the most significant climate change effects are confined to specific regions, including the African Highlands.<ref>{{cite journal | vauthors = Caminade C, Kovats S, Rocklov J, Tompkins AM, Morse AP, Colón-González FJ, Stenlund H, Martens P, Lloyd SJ | display-authors = 6 | title = Impact of climate change on global malaria distribution | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 111 | issue = 9 | pages = 3286–3291 | date = March 2014 | pmid = 24596427 | pmc = 3948226 | doi = 10.1073/pnas.1302089111 | bibcode = 2014PNAS..111.3286C | doi-access = free }}</ref>

Climate change may lead to dramatic increases in the prevalence of a variety of infectious diseases. Beginning in the mid-'70s, an "emergence, resurgence and redistribution of infectious diseases" occurred.<ref name="Epstein">{{cite journal | vauthors = Epstein PR | title = Climate change and infectious disease: stormy weather ahead? | journal = Epidemiology | volume = 13 | issue = 4 | pages = 373–375 | date = July 2002 | pmid = 12094088 | doi = 10.1097/00001648-200207000-00001 | s2cid = 19299458 | doi-access = free }}</ref> Reasons for this are likely multi-causal, dependent on a variety of social, environmental and climatic factors, however, many argue that the "volatility of infectious disease may be one of the earliest biological expressions of climate instability".<ref name="Epstein" /> 

== Mechanisms and pathways ==

{{Further|Effects of climate change on human health}}Infectious diseases (also called [[Pathogen|pathogenic]] diseases) depend on "a pathogen and a person coming into contact, and the extent to which peoples’ resistance is diminished, or the pathogen is strengthened, by a climatic [[hazard]]."<ref name="Mora_2022" /> Climatic hazards, which can be strengthened by climate change, include  warming of land and oceans, [[Heat wave|heatwaves]] and [[Marine heatwave|marine heatwaves]], floods, drought, storms, land cover change, fires and so forth.<ref name="Mora_2022" />

Possible pathways that can increase the infectious disease occurrence and which are affected by climate change include:<ref name="Mora_2022" />

* Climatic hazards bringing pathogens closer to people (e.g. shifts in the geographical range of species)
* Climatic hazards bringing people closer to pathogens (e.g. heatwaves bringing more people to recreational water activities)
* Pathogens strengthened by climatic hazards (e.g. "improved climate suitability for reproduction, acceleration of the life cycle, increasing seasons/length of likely exposure", for example [[Ocean Warming|ocean warming]] can lead to increased [[Vibriosis]] outbreaks)
* People impaired by climatic hazards (e.g. from [[malnutrition]] due to drought conditions)

Infectious diseases that are sensitive to climate can be grouped into: 

* [[Waterborne diseases|water-borne diseases]] (transmitted via viruses or bacteria, e.g.: E. Coli), 
* [[Vector-borne disease|vector-borne diseases]] (transmitted via mosquitos, ticks etc.), and 
* [[food-borne diseases]] (e.g. [[Salmonella]] bacteria, causing [[Salmonellosis]]).<ref name=":16" />{{rp|1107}} 

Climate change is affecting the distribution of these diseases due to the expanding geographic range and seasonality of these diseases and their vectors.<ref name="Romanello2021" />[[Waterborne diseases|{{rp|9}}]]

Though many infectious diseases are affected by changes in climate, vector-borne diseases, such as malaria, dengue fever and leishmaniasis, present the strongest causal relationship. One reason for that is that temperature and rainfall play a key role in the distribution, magnitude, and viral capacity of mosquitoes, who are primary vectors for many vectors borne diseases. Observation and research detect a shift of pests and pathogens in the distribution away from the equator and towards Earth's poles.<ref>{{Cite journal |vauthors=Bebber DP, Ramotowski MA, Gurr SJ |year=2013 |title=Crop pests and pathogens move polewards in a warming world |journal=Nature Climate Change |volume=3 |issue=11 |pages=985–988 |bibcode=2013NatCC...3..985B |doi=10.1038/nclimate1990}}</ref>

=== Changes to the distribution of vectors ===
{{See also|Disease vector|Mosquito-borne disease}}

Climate change affects vector-borne diseases by affecting the survival, distribution and behavior of vectors such as mosquitoes, ticks and rodents.<ref name="Impacts of Climate Change Ch 1 2016">{{Cite book |url=https://health2016.globalchange.gov/downloads |title=The Impacts of Climate Change on Human Health in the United States: A Scientific Assessment |vauthors=Balbus J, Crimmins A, Gamble JL, Easterling DR, Kunkel KE, Saha S, Sarofim MC |publisher=U.S. Global Change Research Program |year=2016 |location=Washington, D.C. |chapter=Ch. 1: Introduction: Climate Change and Human Health |doi=10.7930/J0VX0DFW |access-date=28 June 2020 |chapter-url=https://health2016.globalchange.gov/high/ClimateHealth2016_01_Introduction.pdf |doi-access=free}}</ref>{{Rp|29}} The viruses, bacteria and protozoa are carried by these vectors transferring them from one carrier to another.<ref>{{cite book |url=https://health2016.globalchange.gov/downloads#vectorborne-diseases |title=Climate and Health Assessment |vauthors=Beard C, Eisen R, Barker C, Garofalo J, Hahn M, Hayden M, Monaghan A, Ogden N, Schramm P |date=2016 |chapter=Ch. 5: Vectorborne Diseases. The Impacts of Climate Change on Human Health in the United States: A Scientific Assessment |doi=10.7930/j0765c7v |display-authors=6}}</ref> Vectors and pathogens can adapt to the climate fluctuations by shifting and expanding their geographic ranges, which alter the rate of new cases of disease depending on vector-host interaction, host immunity and pathogen evolution.<ref>{{Cite web |date=9 September 2019 |title=Climate Change and Public Health – Disease Vectors {{!}} CDC |url=https://www.cdc.gov/climateandhealth/effects/vectors.htm |access-date=4 May 2020 |website=www.cdc.gov |language=en-us}}</ref> This means that climate change affects infectious diseases by changing the length of the transmission season and their geographical range.<ref name="Caminade219" />

Climate change is leading to latitudinal and altitudinal temperature increases. Global warming projections indicate that surface air warming for a "high scenario" is 4 C, with a likely range of 2.4–6.4 C by 2100.<ref>{{cite book |author=IPCC |url=http://www.ipcc.ch/publications_and_data/publications_ipcc_fourth_assessment_report_wg2_report_impacts_adaptation_and_vulnerability.htm |title=Climate Change 2007: Impacts, Adaptation, and Vulnerability. |publisher=Cambridge University Press. |year=2007 |location=Cambridge |access-date=30 April 2021 |archive-date=5 October 2018 |archive-url=https://web.archive.org/web/20181005031903/http://www.ipcc.ch/publications_and_data/publications_ipcc_fourth_assessment_report_wg2_report_impacts_adaptation_and_vulnerability.htm |url-status=dead }}</ref> A temperature increase of this size would alter the biology and the ecology of many mosquito vectors and the dynamics of the diseases they transmit such as malaria. 

Changes in climate and global warming have significant influences on the biology and  distribution of [[Vector-borne disease|vector-borne diseases]], [[parasites]], [[Fungus|fungi]], and their associated illnesses. Regional changes resulting from changing weather conditions and patterns within temperate climates will stimulate the reproduction of certain insect species that are vectors for disease. 

One major disease-spreading insect is the [[mosquito]], which can carry diseases like [[malaria]], [[West Nile virus]], and [[dengue fever]]. With regional temperatures changing due to climate change, the range of mosquitos will change as well.<ref>{{Cite web | vauthors = Jordan R |date=March 15, 2019 |title=How dose climate change affect disease |url=https://earth.stanford.edu/news/how-does-climate-change-affect-disease#gs.04lyyi |url-status=live |archive-url=https://web.archive.org/web/20190602101820/https://earth.stanford.edu/news/how-does-climate-change-affect-disease |archive-date=2019-06-02 |access-date=May 6, 2021 |website=Stanford University}}</ref> The range of mosquitoes will move farther north and south, and places will have a longer period of mosquito habitability than at present, leading to an increase in the mosquito population in these areas. This range shift has already been seen in highland Africa. Since 1970, the incidence of malaria in high-elevation areas in East Africa has increased greatly. This has been proven to be caused by the warming of regional climates.<ref name="Ostfeld_2009">{{cite journal | vauthors = Ostfeld RS | title = Climate change and the distribution and intensity of infectious diseases | journal = Ecology | volume = 90 | issue = 4 | pages = 903–905 | date = April 2009 | pmid = 19449683 | doi = 10.1890/08-0659.1 | jstor = 25592576 | bibcode = 2009Ecol...90..903O }}</ref><ref>{{Cite journal | vauthors = Deischstetter P |date=2017 |title=The Effect of Climate Change on Mosquito-Borne Diseases |url=https://www.jstor.org/stable/26411199 |journal=The American Biology Teacher |volume=79 |issue=3 |pages=169–173 |doi=10.1525/abt.2017.79.3.169 |issn=0002-7685 |jstor=26411199 |s2cid=90364501}}</ref>

The vectors of transmission are the major reason for the increased ranges and infection of these diseases. If the vector has a range shift, so do the associated diseases; if the vector increases in activity due to changes in climate, then there is an effect on the transmission of disease.<ref name="Ostfeld_2009" /> However it will be hard to classify exactly why the range shifts or an increase in infection rates occurs as there are many other factors to consider besides climate change, such as [[human migration]], [[poverty]], [[infrastructure]] quality, and [[Land use|land usage]]; but climate change is still potentially a key factor.<ref name="Cooney_2011">{{cite journal | vauthors = Cooney CM | title = Climate change & infectious disease: is the future here? | journal = Environmental Health Perspectives | volume = 119 | issue = 9 | pages = a394–a397 | date = September 2011 | pmid = 21885367 | pmc = 3230419 | doi = 10.1289/ehp.119-a394 | jstor = 41263126 }}</ref>

Environmental changes, [[climate variability]], and climate change are such factors that could affect biology and [[disease ecology]] of Anopheles vectors and their [[disease transmission]] potential.<ref name="Afrane">{{cite journal | vauthors = Afrane YA, Githeko AK, Yan G | title = The ecology of Anopheles mosquitoes under climate change: case studies from the effects of deforestation in East African highlands | journal = Annals of the New York Academy of Sciences | volume = 1249 | issue = 1 | pages = 204–210 | date = February 2012 | pmid = 22320421 | pmc = 3767301 | doi = 10.1111/j.1749-6632.2011.06432.x | bibcode = 2012NYASA1249..204A }}</ref>

Anopheles mosquitoes in highland areas are to experience a larger shift in their metabolic rate due to climate change. This climate change is due to the deforestation in the highland areas where these mosquitos' dwell. When the temperature rises, the [[larvae]] take a shorter time to mature<ref>{{cite journal | vauthors = Munga S, Minakawa N, Zhou G, Githeko AK, Yan G | title = Survivorship of immature stages of Anopheles gambiae s.l. (Diptera: Culicidae) in natural habitats in western Kenya highlands | journal = Journal of Medical Entomology | volume = 44 | issue = 5 | pages = 758–764 | date = September 2007 | pmid = 17915505 | doi = 10.1603/0022-2585(2007)44[758:SOISOA]2.0.CO;2 | s2cid = 10278388 }}</ref> and, consequently, a greater capacity to produce more offspring. In turn this could potentially lead to an increase in malaria transmission when infected humans are available.

Environmental changes such as deforestation could also increase local temperatures in the highlands thus could enhance the vector capacity of the anopheles.<ref name="Afrane" /> Anopheles mosquitoes are responsible for the transmission of a number of diseases in the world, such as, malaria, [[lymphatic filariasis]] and viruses that can cause such ailments, like the [[O'nyong'nyong virus]].<ref name="Afrane" />

=== Increased water temperature ===
High temperatures can alter the survival, replication, and virulence of a pathogen.<ref name="(Levy et al., 2018)" /> Higher temperatures can also increase the pathogen yields in animal reservoirs. During the warmer summer months an increase in yield of bacteria from drinking water delivery systems has been recorded. During times of warmer temperatures water consumption rates are also typically higher. These together increase the probability of pathogen ingestion and infection.<ref name="(Levy et al., 2016)">{{cite journal |vauthors=Levy K, Woster AP, Goldstein RS, Carlton EJ |date=May 2016 |title=Untangling the Impacts of Climate Change on Waterborne Diseases: a Systematic Review of Relationships between Diarrheal Diseases and Temperature, Rainfall, Flooding, and Drought |journal=Environmental Science & Technology |volume=50 |issue=10 |pages=4905–4922 |bibcode=2016EnST...50.4905L |doi=10.1021/acs.est.5b06186 |pmc=5468171 |pmid=27058059}}</ref> 

With an increase in not only temperature, but also higher nutrient concentrations due to runoff there will be an increase in [[cyanobacteria]]l blooms.<ref name="(Hunter, 2003)">{{cite journal |vauthors=Hunter PR |date=2003 |title=Climate change and waterborne and vector-borne disease |journal=Journal of Applied Microbiology |volume=94 |issue=s1 |pages=37S–46S |doi=10.1046/j.1365-2672.94.s1.5.x |pmid=12675935 |doi-access=free}}</ref>

{{excerpt|Effects of climate change on human health#Harmful algal blooms in oceans and lakes}}

===Changes in precipitation and water cycle===
{{Further|Effects of climate change|Effects of climate change on the water cycle|Flood#Health impacts}}

Climate change is forecast to have substantial effects on the [[water cycle]], with an increase in both frequency and intensity of droughts and heavy precipitation events.<ref name="(Levy et al., 2018)" /> 

A literature review in 2016 found that generally there is an increase in [[Diarrhea|diarrheal]] disease (except for viral diarrheal disease) during or after certain weather conditions: elevated ambient temperature, heavy rainfall, and flooding.<ref name="Levy_2016">{{cite journal | vauthors = Levy K, Woster AP, Goldstein RS, Carlton EJ | title = Untangling the Impacts of Climate Change on Waterborne Diseases: a Systematic Review of Relationships between Diarrheal Diseases and Temperature, Rainfall, Flooding, and Drought | journal = Environmental Science & Technology | volume = 50 | issue = 10 | pages = 4905–4922 | date = May 2016 | pmid = 27058059 | pmc = 5468171 | doi = 10.1021/acs.est.5b06186 | bibcode = 2016EnST...50.4905L }}</ref> These three weather conditions are predicted to increase (or to intensify) with climate change in future. There is already now a high current baseline rate of the diarrheal diseases in developing countries. Climate change therefore poses a real risk of an uptick in these diseases for those regions.<ref name="Levy_2016" />

{{excerpt|Effects of climate change#Floods}}

== Selected examples of relevant infectious diseases in humans ==
{{See also|List of diseases spread by invertebrates|List of insect-borne diseases|Mosquito-borne disease}}
=== Malaria ===
{{Further|Malaria#Climate change}}
[[File:Malaria world map-Deaths per million persons-WHO2012.svg|thumb|upright=1.3|Deaths due to malaria per million persons in 2012 {{Div col|small=yes|colwidth=10em}}{{legend|#ffff20|0–0}}{{legend|#ffa020|1–2}}{{legend|#ff9a20|3–54}}{{legend|#f08015|55–325}}{{legend|#e06815|326–679}}{{legend|#d85010|680–949}}{{legend|#d02010|950–1,358}}{{div col end}}]]
[[File:World-map-of-past-and-current-malaria-prevalence-world-development-report-2009.png|thumb|upright=1.3|Past and current malaria prevalence in 2009]]
Increased rainfall could increase the number of [[mosquito]]s indirectly by expanding larval habitat and food supply. Malaria, which kills about 300,000 children (under age 5) annually, poses an [[imminent threat]] through temperature increase.<ref name="malaria">{{cite journal | vauthors = Patz JA, Olson SH | title = Malaria risk and temperature: influences from global climate change and local land use practices | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 103 | issue = 15 | pages = 5635–5636 | date = April 2006 | pmid = 16595623 | pmc = 1458623 | doi = 10.1073/pnas.0601493103 | doi-access = free | bibcode = 2006PNAS..103.5635P }}</ref> Models suggest, conservatively, that the risk of malaria will increase 5–15% by 2100 due to climate change.<ref name="Bhattacharya">{{Cite journal | vauthors = Bhattacharya S, Sharma C, Dhiman R, Mitra A |year=2006|title=Climate Change and Malaria in India|journal=[[Current Science]]|volume=90|issue=3|pages=369–375}}</ref> In Africa alone, according to the MARA Project (Mapping Malaria Risk in Africa),<ref name="mara">{{cite web |url= http://www.mara.org.za/pdfmaps/NgaSeasonality.PDF |archive-url= https://web.archive.org/web/20051210185537/http://www.mara.org.za/pdfmaps/NgaSeasonality.PDF |url-status=dead |archive-date= 10 December 2005 |title= Nigeria: Duration of the Malaria Transmission Season |access-date= 24 January 2007 |date= July 2001 |work= mara.org.za |publisher= MARA/ARMA (Mapping Malaria Risk in Africa / Atlas du Risque de la Malaria en Afrique) }}</ref> there is a projected increase of 16–28% in person-month exposures to malaria by 2100.<ref name="Patz_2005">{{cite journal | vauthors = Patz JA, Campbell-Lendrum D, Holloway T, Foley JA | title = Impact of regional climate change on human health | journal = Nature | volume = 438 | issue = 7066 | pages = 310–317 | date = November 2005 | pmid = 16292302 | doi = 10.1038/nature04188 | s2cid = 285589 | bibcode = 2005Natur.438..310P }}</ref>

Climate is an influential driving force of vector-borne diseases such as malaria. Malaria is especially susceptible to the effects of climate change because mosquitoes lack the mechanisms to regulate their internal temperature. This implies that there is a limited range of climatic conditions within which the pathogen (malaria) and vector (a mosquito) can survive, reproduce, and infect hosts.<ref name="infectious">{{cite journal| vauthors = Rawshan AB, Er A, Raja D, Pereira JJ |year=2010|title=Malaria and Climate Change: Discussion on Economic Impacts|journal=[[American Journal of Environmental Sciences]]|volume=7|issue=1|pages=65–74|doi=10.3844/ajessp.2011.73.82}}</ref> Vector-borne diseases, such as malaria, have distinctive characteristics that determine [[pathogenicity]]. These include the survival and reproduction rate of the vector, the level of vector activity (i.e. the biting or feeding rate), and the development and reproduction rate of the pathogen within the vector or host.<ref name="infectious" /> Changes in climate factors substantially affect reproduction, development, distribution, and seasonal transmissions of malaria.

Malaria is a mosquito-borne parasitic disease that infects humans and other animals caused by microorganisms in the [[Plasmodium]] family. It begins with a bite from an infected female mosquito, which introduces the parasite through its saliva and into the infected host's circulatory system. It then travels through the bloodstream into the liver, where it can mature and reproduce.<ref name="Lancet">{{cite journal | vauthors = Greenwood BM, Bojang K, Whitty CJ, Targett GA | title = Malaria | journal = Lancet | volume = 365 | issue = 9469 | pages = 1487–1498 | date = 23 April 2005 | pmid = 15850634 | doi = 10.1016/S0140-6736(05)66420-3 | s2cid = 208987634 }}</ref>

=== Dengue fever ===
[[File:Disease_Vector.jpg|thumb|This figure shows how the [[Flavivirus]] is carried by [[Mosquito|mosquitos]] in the [[West Nile virus]] and [[Dengue fever]]. The mosquito would be considered a [[disease vector]].]]
[[Dengue fever]] is an infectious disease caused by [[dengue virus]]es known to be in the tropical regions.<ref name="Dengue and Severe Dengue">{{cite web|year=2012|title=Dengue and Severe Dengue, Fact Sheet|url=https://www.who.int/mediacentre/factsheets/fs117/en/|work=Media Centre|publisher=World Health Organization}}</ref> It is transmitted by the mosquito [[Aedes]], or A. aegypti.<ref>{{cite journal | vauthors = Simmons CP, Farrar JJ, Nguyen VV, Wills B | title = Dengue | journal = The New England Journal of Medicine | volume = 366 | issue = 15 | pages = 1423–1432 | date = April 2012 | pmid = 22494122 | doi = 10.1056/NEJMra1110265 | hdl-access = free | hdl = 11343/191104 }}</ref> Dengue incidence has increased in the last few decades and is projected to continue to do so with changing climate conditions.<ref>{{cite journal | vauthors = Banu S, Hu W, Guo Y, Hurst C, Tong S | title = Projecting the impact of climate change on dengue transmission in Dhaka, Bangladesh | journal = Environment International | volume = 63 | issue = | pages = 137–42 | date = February 2014 | pmid = 24291765 | doi = 10.1016/j.envint.2013.11.002 | s2cid = 6874626 | url = https://eprints.qut.edu.au/67037/10/67037d.pdf}}</ref> Dengue can be fatal.<ref>{{Cite web|title=WHO {{!}} The human|url=https://www.who.int/denguecontrol/human/en/|access-date=25 July 2019|website=WHO}}</ref><ref name="www.who.int">{{Cite web|title=Dengue and severe dengue|url=https://www.who.int/news-room/fact-sheets/detail/dengue-and-severe-dengue|access-date=6 May 2020|website=www.who.int|language=en}}</ref> Dengue fever is spread by the bite of the female mosquito known as ''Aedes aegypti.'' The female mosquito is a highly effective vector of this disease.<ref>{{Cite web|title=WHO {{!}} Dengue/Severe dengue frequently asked questions|url=https://www.who.int/denguecontrol/faq/en/|archive-url=https://web.archive.org/web/20121025233710/http://www.who.int/denguecontrol/faq/en/|url-status=dead|archive-date=25 October 2012|access-date=25 July 2019|website=WHO}}</ref>

The evidence for the spread of dengue fever is that climate change is altering the geographic range and seasonality of the mosquito that can carry dengue. Because there are multiple drivers of transmission, it is easier to model and project changes in the geographic range and seasonality. The drivers for the recent spread of this disease are globalization, trade, urbanization, population growth, increased international travel, and climate change.<ref name="Ebi_2016">{{cite journal | vauthors = Ebi KL, Nealon J | title = Dengue in a changing climate | journal = Environmental Research | volume = 151 | issue =  | pages = 115–123 | date = November 2016 | pmid = 27475051 | doi = 10.1016/j.envres.2016.07.026 | bibcode = 2016ER....151..115E | doi-access = free }}</ref><ref>{{cite encyclopedia |year=2010 |title=Human and Medical Virology: Dengue Viruses |encyclopedia=Desk Encyclopedia of Human and Medical Virology |publisher=Academic Press |url=https://books.google.com/books?id=nsh48WKIbhQC&pg=PA372 |pages=372–382 |isbn=978-0-12-378559-6 |vauthors=Gubler DJ |veditors=Mahy BW, van Regenmortel MH}}</ref> The same trends also led to the spread of different serotypes of the disease to new areas, and to the emergence of [[dengue hemorrhagic fever]]. 

The World Health Organization (WHO) has reported an increase from a thousand to one million confirmed cases between 1955 and 2007.<ref name="www.who.int" /> The presence and number of ''Aedes aegypti'' mosquitoes is strongly influenced by the amount of water-bearing containers or pockets of stagnant water in an area, daily temperature and variation in temperature, moisture, and solar radiation.<ref name="Patz_2005" /> While dengue fever is primarily considered a [[Tropical disease|tropical and subtropical disease]], the geographic ranges of the Aedes aegypti are expanding. The cases of dengue fever have increased dramatically since the 1970s and it continues to become more prevalent.<ref name="Dengue and Severe Dengue" />

Dengue is ranked as the most important vector-borne viral disease in the world. An estimated 50–100&nbsp;million dengue fever infections occur annually. In just the past 50 years, transmission has increased drastically with new cases of the disease (incidence) increasing 30-fold.<ref name="Ebi_2016" /> The number of reported cases has continually increased along with dengue spreading to new areas.

=== Tick borne disease ===
[[File:Adult_deer_tick(cropped).jpg|thumb|The [[Ixodes scapularis|deer tick]], a vector for [[Lyme disease]] pathogens]]
[[File:Tick_on_human_head.jpg|right|thumb|A tick crawling on a human head in a wooded area near [[LeRoy, Michigan]].]]
[[Tick-borne disease]], which affect humans and other animals, are caused by infectious agents [[Vector (epidemiology)|transmitted by]] [[tick]] bites. A high humidity of greater than 85% is ideal for a tick to start and finish its life cycle.<ref>{{cite journal | vauthors = Süss J, Klaus C, Gerstengarbe FW, Werner PC | title = What makes ticks tick? Climate change, ticks, and tick-borne diseases | journal = Journal of Travel Medicine | volume = 15 | issue = 1 | pages = 39–45 | date = 1 January 2008 | pmid = 18217868 | doi = 10.1111/j.1708-8305.2007.00176.x | doi-access = free }}</ref> Studies have indicated that temperature and vapor play a significant role in determining the range for tick population. More specifically, maximum temperature has been found to play the most influential variable in sustaining tick populations.<ref name="Brownstein_2003">{{cite journal | vauthors = Brownstein JS, Holford TR, Fish D | title = A climate-based model predicts the spatial distribution of the Lyme disease vector Ixodes scapularis in the United States | journal = Environmental Health Perspectives | volume = 111 | issue = 9 | pages = 1152–1157 | date = July 2003 | pmid = 12842766 | pmc = 1241567 | doi = 10.1289/ehp.6052 }}</ref> Higher temperatures augment both hatching and developmental rates while hindering overall survival. Temperature is so important to overall survival that an average monthly minimum temperature of below -7&nbsp;°C in the winter can prevent an area from maintaining established populations.<ref name="Brownstein_2003" />

The effect of climate on the tick life cycle is one of the more difficult projections to make in relation to climate and vector-borne disease. Unlike other vectors, tick life cycles span multiple seasons as they mature from larva to nymph to adult.<ref>{{Cite web|url=https://health2016.globalchange.gov/climate-and-health-assessment/vectorborne-diseases/boxes/life-cycle-blacklegged-ticks-ixodes|title=Life Cycle of Blacklegged Ticks, Ixodes scapularis {{!}} Climate and Health Assessment|last=USGCRP|website=health2016.globalchange.gov|language=en|access-date=29 October 2018|archive-date=30 October 2018|archive-url=https://web.archive.org/web/20181030035833/https://health2016.globalchange.gov/climate-and-health-assessment/vectorborne-diseases/boxes/life-cycle-blacklegged-ticks-ixodes|url-status=dead}}</ref> Further, infection and spread of diseases such as [[Lyme disease]] happen across the multiple stages and different classes of vertebrate hosts, adding additional variables to consider. Although it is a European species from the Lyme borreliosis spirochetes, ''Borrelia garinii'' was documented from infected ticks on seabirds in North America.<ref>{{cite journal | vauthors = Munro HJ, Ogden NH, Mechai S, Lindsay LR, Robertson GJ, Whitney H, Lang AS | title = Genetic diversity of Borrelia garinii from Ixodes uriae collected in seabird colonies of the northwestern Atlantic Ocean | journal = Ticks and Tick-Borne Diseases | volume = 10 | issue = 6 | pages = 101255 | date = October 2019 | pmid = 31280947 | doi = 10.1016/j.ttbdis.2019.06.014 | s2cid = 195829855 }}</ref> Further research is needed to improve evolutionary models predicting distributional changes in this tick-borne system in the face of climate change.<ref name="sciencedirect.com">{{cite journal | vauthors = Wolcott KA, Margos G, Fingerle V, Becker NS | title = Host association of Borrelia burgdorferi sensu lato: A review | journal = Ticks and Tick-Borne Diseases | volume = 12 | issue = 5 | pages = 101766 | date = September 2021 | pmid = 34161868 | doi = 10.1016/j.ttbdis.2021.101766 }}</ref> Infection of ticks happen in the larval/nymph stage (after the first blood meal) when they are exposed to ''Borrelia burgdorferi'' (the spirochete responsible for Lyme disease<ref name="sciencedirect.com"/>), but transmission to humans doesn't occur until the adult stages.

The expansion of tick populations is concurrent with global climatic change. Species distribution models of recent years indicate that the deer tick, known as ''I. scapularis,'' is pushing its distribution to higher latitudes of the Northeastern United States and Canada, as well as pushing and maintaining populations in the South Central and Northern Midwest regions of the United States.<ref name="Esteve-Gassent 38–64">{{cite journal | vauthors = Esteve-Gassent MD, Castro-Arellano I, Feria-Arroyo TP, Patino R, Li AY, Medina RF, de León AA, Rodríguez-Vivas RI | title = Translating Ecology, Physiology, Biochemistry, and Population Genetics Research to Meet the Challenge of Tick and Tick-Borne Diseases in North America | display-authors = 6 | journal = Archives of Insect Biochemistry and Physiology | volume = 92 | issue = 1 | pages = 38–64 | date = May 2016 | pmid = 27062414 | pmc = 4844827 | doi = 10.1002/arch.21327 }}</ref> Climate models project further expansion of tick habit north into Canada as progressing Northwest from the Northeastern United States. Additionally, however, tick populations are expected to retreat from the Southeastern coast of the U.S., but this has not yet been observed.<ref>{{Cite book|url=https://books.google.com/books?id=U0E1CAAAQBAJ&q=luber+lemry+climate+health&pg=PR11|title=Global Climate Change and Human Health: From Science to Practice| vauthors = Luber G, Lemery J |date=2 November 2015|publisher=John Wiley & Sons|isbn=978-1-118-50557-1|language=en}}</ref> It's estimated that coinciding with this expansion, increased average temperatures may double tick populations by 2020 as well as bring an earlier start to the tick exposure season.<ref>{{cite journal | vauthors = Monaghan AJ, Moore SM, Sampson KM, Beard CB, Eisen RJ | title = Climate change influences on the annual onset of Lyme disease in the United States | journal = Ticks and Tick-Borne Diseases | volume = 6 | issue = 5 | pages = 615–622 | date = July 2015 | pmid = 26025268 | pmc = 4631020 | doi = 10.1016/j.ttbdis.2015.05.005 | bibcode = 2015AGUFMGC13L..07M }}</ref><ref name="Esteve-Gassent 38–64"/>

In the face of these expanding threats, strong collaboration between government officials and environmental scientists is necessary for advancing preventive and reactive response measures. Without acknowledging the climate changes that make environments more habitable for disease carriers, policy and infrastructure will lag behind vector borne disease spread.<ref>{{Cite news|url=https://www.publicintegrity.org/2018/08/06/21999/disease-bearing-ticks-head-north-weak-government-response-threatens-public-health|title=As disease-bearing ticks head north, weak government response threatens public health|work=Center for Public Integrity|access-date=29 October 2018}}</ref> 

In the United States, the Centers for Disease Control and Prevention (CDC) is conducting a grant program called Building Resilience Against Climate Effects (BRACE) which details a 5 step process for combating climate effects like tick borne disease spread.<ref>{{Cite web|url=https://www.cdc.gov/climateandhealth/BRACE.htm|title=CDC – Climate and Health – CDC's Building Resilience Against Climate Effects (BRACE) Framework| work = National Center for Environmental Health| publisher = U.S. Centers for Disease Control and Prevention |language=en-us|access-date=29 October 2018}}</ref> 

=== Leishmaniasis ===
{{Further|Leishmaniasis}}

As in other [[vector-borne disease]]s, one of the reasons climate changes can affect the incidence of [[leishmaniasis]] is the susceptibility of the [[sandfly]] vectors to changes in temperature, rainfall and humidity; these conditions will alter their range of distribution and seasonality.<ref name="World Health Organization_2020">{{cite web |date=March 2020 |title=Leishmaniasis |url=https://www.who.int/en/news-room/fact-sheets/detail/leishmaniasis |access-date=25 November 2020 |website=World Health Organization}}</ref> For example, modelling studies have predicted that climate change will increase suitable conditions for ''[[Phlebotomus]]'' vector species in Central Europe.<ref>{{cite journal | vauthors = Fischer D, Moeller P, Thomas SM, Naucke TJ, Beierkuhnlein C | title = Combining climatic projections and dispersal ability: a method for estimating the responses of sandfly vector species to climate change | journal = PLOS Neglected Tropical Diseases | volume = 5 | issue = 11 | pages = e1407 | date = November 2011 | pmid = 22140590 | pmc = 3226457 | doi = 10.1371/journal.pntd.0001407 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Koch LK, Kochmann J, Klimpel S, Cunze S | title = Modeling the climatic suitability of leishmaniasis vector species in Europe | journal = Scientific Reports | volume = 7 | issue = 1 | pages = 13325 | date = October 2017 | pmid = 29042642 | pmc = 5645347 | doi = 10.1038/s41598-017-13822-1 | bibcode = 2017NatSR...713325K }}</ref> Another model that looked at the distribution of ''[[Lutzomyia longipalpis]]'', an important visceral leishmaniasis vector, suggested an increased range of this species in the Amazon Basin.<ref>{{cite journal | vauthors = Peterson AT, Campbell LP, Moo-Llanes DA, Travi B, González C, Ferro MC, Ferreira GE, Brandão-Filho SP, Cupolillo E, Ramsey J, Leffer AM, Pech-May A, Shaw JJ | display-authors = 6 | title = Influences of climate change on the potential distribution of Lutzomyia longipalpis sensu lato (Psychodidae: Phlebotominae) | journal = International Journal for Parasitology | volume = 47 | issue = 10–11 | pages = 667–674 | date = September 2017 | pmid = 28668326 | doi = 10.1016/j.ijpara.2017.04.007 | hdl = 11336/43578 | hdl-access = free }}</ref> A different study model that factored data on climate, policy and [[Socioeconomics|socio-economic]] changes of land use, found that the effects were different for cutaneous and visceral leishmaniasis, emphasizing the importance of considering each disease and region separately.<ref>{{cite journal | vauthors = Purse BV, Masante D, Golding N, Pigott D, Day JC, Ibañez-Bernal S, Kolb M, Jones L | display-authors = 6 | title = How will climate change pathways and mitigation options alter incidence of vector-borne diseases? A framework for leishmaniasis in South and Meso-America | journal = PLOS ONE | volume = 12 | issue = 10 | pages = e0183583 | date = 2017 | pmid = 29020041 | pmc = 5636069 | doi = 10.1371/journal.pone.0183583 | doi-access = free | bibcode = 2017PLoSO..1283583P }}</ref>

Parasite development inside the sand can also be affected by temperature changes. For instance, ''Leishmania peruviana'' infections were lost during sand defecation when the infected vector was kept at higher temperatures, whereas in the same experiment ''[[Leishmania infantum]]'' and ''[[Leishmania braziliensis]]'' temperature seemed to make no difference.<ref>{{cite journal | vauthors = Hlavacova J, Votypka J, Volf P | title = The effect of temperature on Leishmania (Kinetoplastida: Trypanosomatidae) development in sand flies | journal = Journal of Medical Entomology | volume = 50 | issue = 5 | pages = 955–958 | date = September 2013 | pmid = 24180098 | doi = 10.1603/ME13053 | doi-access = free }}</ref>

Leishmaniasis is a [[Neglected tropical diseases|neglected tropical disease]], caused by parasites of the genus ''[[Leishmania]]'' and transmitted by sandflies; it is distributed mostly in tropical and subtropical regions around the world, wherever the sand fly vector and reservoir hosts are present.<ref name="World Health Organization">{{cite web |title=Report on Global Surveillance of Epidemic-prone Infectious Diseases – Leishmaniasis |url=https://www.who.int/csr/resources/publications/CSR_ISR_2000_1leish/en/ |url-status=dead |archive-url=https://web.archive.org/web/20040718084120/http://www.who.int/csr/resources/publications/CSR_ISR_2000_1leish/en/ |archive-date=18 July 2004 |access-date=25 November 2020 |website=World Health Organization}}</ref> The WHO estimates 12 million people around the world are living with leishmaniasis.<ref name="World Health Organization" /> [[Risk factor]]s for the spread of this disease include poverty, urbanization, [[deforestation]], and climate change.<ref name="World Health Organization_2020" /><ref>{{cite journal | vauthors = González C, Wang O, Strutz SE, González-Salazar C, Sánchez-Cordero V, Sarkar S | title = Climate change and risk of leishmaniasis in north america: predictions from ecological niche models of vector and reservoir species | journal = PLOS Neglected Tropical Diseases | volume = 4 | issue = 1 | pages = e585 | date = January 2010 | pmid = 20098495 | pmc = 2799657 | doi = 10.1371/journal.pntd.0000585 | doi-access = free }}</ref>

=== Ebola ===
The [[Ebola virus]] has been infecting people from time to time, leading to outbreaks in several African countries. The average case fatality rate of the Ebola virus is approximately 40% and there have been more than 28,600 cases with 11,310 deaths.<ref>{{Cite web |date=5 February 2020 |title=Ebola (Ebola Virus Disease) {{!}} CDC |url=https://www.cdc.gov/vhf/ebola/index.html |access-date=6 May 2020 |website=www.cdc.gov |language=en-us}}</ref> Many researchers are linking deforestation to the disease, observing that change in the landscape increases wildlife contact with humans.<ref name="Christensen_2019">{{Cite web |date=15 October 2019 |title=Climate crisis raises risk of more Ebola outbreaks |url=https://www.cnn.com/2019/10/15/health/climate-crisis-ebola-risks/index.html |access-date=6 May 2020 |website=CNN |vauthors=Christensen J}}</ref> 

Recent studies are holding climate change indirectly liable for the uptick in Ebola: Seasonal droughts alongside strong winds, thunderstorms, heat waves, floods, landslides, and a change in rainfall patterns also impact wildlife migration. These conditions pull them away from their natural environment and closer to human proximity.<ref>{{Cite web |date=14 August 2014 |title=Ebola and Climate Change: How Are They Connected? |url=https://www.ecowatch.com/ebola-and-climate-change-how-are-they-connected-1881942860.html |access-date=6 May 2020 |website=EcoWatch |language=en}}</ref> One example of an Ebola outbreak caused by climate change or a shift in nature was seen during the drought of Central Africa. This ultimately amplified food insecurity leading West African communities to eat animals such as bats who were infected with the virus.<ref name="Christensen_2019" />

=== Zika fever ===
{{Further|Zika virus|Zika fever}}

[[Zika virus]], a vector-borne virus was historically presented in cluster outbreaks in the tropical regions of Africa and Asia.<ref>{{cite journal | vauthors = Plourde AR, Bloch EM | title = A Literature Review of Zika Virus | journal = Emerging Infectious Diseases | volume = 22 | issue = 7 | pages = 1185–1192 | date = July 2016 | pmid = 27070380 | pmc = 4918175 | doi = 10.3201/eid2207.151990 }}</ref> [[Zika fever]] epidemics have affected larger populations including Micronesia and South Pacific Islands in 2007, and the Americas in 2013.<ref>{{cite journal | vauthors = Zhang Q, Sun K, Chinazzi M, Pastore Y, Piontti A, Dean NE, Rojas DP, Merler S, Mistry D, Poletti P, Rossi L, Bray M, Halloran ME, Longini IM, Vespignani A | display-authors = 6 | title = Spread of Zika virus in the Americas | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 114 | issue = 22 | pages = E4334–E4343 | date = May 2017 | pmid = 28442561 | pmc = 5465916 | doi = 10.1073/pnas.1620161114 | doi-access = free | bibcode = 2017PNAS..114E4334Z }}</ref> Brazil has experienced one of the largest outbreaks of Zika virus with approximately 1.5&nbsp;million cases reported in 2015.<ref>{{Cite journal |vauthors=Moghadam SR, Bayrami S, Moghadam SJ, Golrokhi R, Pahlaviani FG, SeyedAlinaghi S |date=1 December 2016 |title=Zika virus: A review of literature |journal=Asian Pacific Journal of Tropical Biomedicine |language=en |volume=6 |issue=12 |pages=989–994 |doi=10.1016/j.apjtb.2016.09.007 |s2cid=79313409 |issn=2221-1691|doi-access=free }}</ref> Pregnant women infected with Zika virus are at a higher risk of giving birth to children with congenital malformations, including microcephaly.<ref>{{Cite web |title=Zika virus |url=https://www.who.int/news-room/fact-sheets/detail/zika-virus |access-date=27 January 2023 |website=www.who.int |language=en}}</ref> 

In the context of climate change and temperature rise, it is predicted that Zika virus will affect more than 1.3&nbsp;billion people by 2050.<ref>{{Cite web |date=11 March 2021 |title=Warming temperatures could expose more than 1.3 billion new people to Zika virus risk by 2050 |url=https://www.ceid.uga.edu/2021/03/11/warming-temperatures-could-expose-more-than-1-3-billion-new-people-to-zika-virus-risk-by-2050/ |access-date=27 January 2023 |website=CEID |language=en-US}}</ref> This is largely due to the expansion of environments conducive to vector growth and life cycles, such as those with temperatures ranging from 23.9&nbsp;°C to 34&nbsp;°C.<ref>{{Cite web |date=11 March 2021 |title=Warming temperatures could expose more than 1.3 billion new people to Zika virus risk by 2050 |url=https://www.ceid.uga.edu/2021/03/11/warming-temperatures-could-expose-more-than-1-3-billion-new-people-to-zika-virus-risk-by-2050/ |access-date=27 January 2023 |website=CEID |language=en-US}}</ref> Mosquito behaviors are also affected by the change in temperature including increased breeding and biting rates.<ref>{{cite journal | vauthors = Epstein PR | title = Climate change and human health | journal = The New England Journal of Medicine | volume = 353 | issue = 14 | pages = 1433–1436 | date = October 2005 | pmid = 16207843 | doi = 10.1056/NEJMp058079 | doi-access = free }}</ref> Furthermore, extreme climate patterns, including drought, floods and heatwaves are known to exacerbate the proliferation of mosquito breeding ground and as a result, escalate the rate of virus-borne diseases.<ref>{{Cite web |title=Explainer: How climate change is amplifying mosquito-borne diseases |url=https://www.worldmosquitoprogram.org/en/news-stories/stories/explainer-how-climate-change-amplifying-mosquito-borne-diseases |access-date=27 January 2023 |website=World Mosquito Program |language=en}}</ref> 

=== COVID-19 ===
{{Further|Origin of COVID-19}}

There is no direct evidence that the spread of [[COVID-19]] is worsened or is caused by climate change, although investigations continue. {{As of|2020||}}, the [[World Health Organization]] summarized the current knowledge about the issue as follows: "There is no evidence of a direct connection between climate change and the emergence or transmission of COVID-19 disease. [...] However, climate change may indirectly affect the COVID-19 response, as it undermines environmental determinants of health, and places additional stress on health systems."<ref>{{cite web |title=Coronavirus disease (COVID-19): Climate change |url=https://www.who.int/news-room/q-a-detail/coronavirus-disease-covid-19-climate-change#:~:text=Will%20climate%20change%20make%20COVID,reducing%20transmission%20and%20treating%20patients. |access-date=24 November 2020 |website=World Health Organization}}</ref>

A 2021 study found possible links between climate change and transmission of COVID-19 by bats.<ref name="Beyer_2021">{{cite journal | vauthors = Beyer RM, Manica A, Mora C | title = Shifts in global bat diversity suggest a possible role of climate change in the emergence of SARS-CoV-1 and SARS-CoV-2 | journal = The Science of the Total Environment | volume = 767 | pages = 145413 | date = May 2021 | pmid = 33558040 | pmc = 7837611 | doi = 10.1016/j.scitotenv.2021.145413 | bibcode = 2021ScTEn.767n5413B | doi-access = free }}</ref> The authors found that climate-driven changes in the distribution and richness of bat species increased the likelihood of bat-borne coronaviruses in the Yunnan province, Myanmar, and Laos.<ref name="Beyer_2021" /> This region was also the habitat of Sunda pangolins and masked palm civits which were suspected as intermediate hosts of COVID-19 between bats and humans.<ref name="Beyer_2021" /> The authors suggest, therefore, that climate change possibly contributed to some extent to the emergence of the pandemic.<ref name="Beyer_2021" /><ref>{{cite web |title=Climate Change Could Have Played A Role In The Covid-19 Outbreak |url=https://www.forbes.com/sites/davidbressan/2021/02/08/climate-change-could-have-played-a-role-in-the-covid-19-outbreak/ |access-date=9 February 2021 |website=Forbes |vauthors=Bressan D}}</ref>

Climate changed might induce changes to bat habitats which may have driven them closer to populated areas.<ref name="Gudipati_2020">{{cite journal | vauthors = Gudipati S, Zervos M, Herc E | title = Can the One Health Approach Save Us from the Emergence and Reemergence of Infectious Pathogens in the Era of Climate Change: Implications for Antimicrobial Resistance? | journal = Antibiotics | volume = 9 | issue = 9 | page = 599 | date = September 2020 | pmid = 32937739 | pmc = 7557833 | doi = 10.3390/antibiotics9090599 | doi-access = free }}</ref> Increased aridity and drought periods are predicted to push bats out of their endemic areas and into populated areas.<ref name="Gudipati_2020" /> This creates a knock-on effect of increasing their interactions with humans and hence the likelihood of zoonotic disease transfer.<ref name="Gudipati_2020" />

=== Vibrio infections ===
{{See also|Vibrio}}
Scientist expect that disease outbreaks caused by [[vibrio]] (in particular the bacterium that causes [[cholera]], called [[vibrio cholerae]]) are increasing in occurrence and intensity.<ref name=":16" />{{rp|1107}} One reason is that the area of coastline with suitable conditions for vibrio bacteria has increased due to changes in [[sea surface temperature]] and sea surface salinity caused by climate change.<ref name="Romanello2021" />[[Waterborne diseases|{{rp|12}}]] These pathogens can cause [[gastroenteritis]], [[cholera]], wound infections, and [[sepsis]]. It has been observed that in the period of 2011–21, the "area of coastline suitable for Vibrio bacterial transmission has increased by 35% in the [[Baltic states|Baltics]], 25% in the Atlantic Northeast, and 4% in the Pacific Northwest.<ref name="Romanello2021" />[[Waterborne diseases|{{rp|12}}]] Furthermore, the increasing occurrence of higher temperature days, heavy rainfall events and flooding due to climate change could lead to an increase in cholera risks.<ref name=":16" />{{rp|1045}}

Vibrio illnesses are  [[Waterborne diseases|waterborne disease]] and are increasing worldwide. Vibrio infections are recently being reported where historically it did not occur. The warming climate seems to be playing a substantial role in the increase in cases and area of occurrence.<ref name="(Walker, 2018)2">{{cite journal | vauthors = Walker JT | title = The influence of climate change on waterborne disease and Legionella: a review | journal = Perspectives in Public Health | volume = 138 | issue = 5 | pages = 282–286 | date = September 2018 | pmid = 30156484 | doi = 10.1177/1757913918791198 | s2cid = 52115812 }}</ref>

Vibrio infections are caused by consuming raw or undercooked seafood, or by exposing an open wound to [[Contamination|contaminated]] sea water. Vibrio infections are most likely to occur during the warm season, May through October.<ref name="CDC2">{{Cite web |date=2019-03-08 |title=Vibrio Species Causing Vibriosis {{!}} Vibrio Illness (Vibriosis) {{!}} CDC |url=https://www.cdc.gov/vibrio/index.html |access-date=2021-01-17 |website=www.cdc.gov |language=en-us}}</ref>

=== Skin Rashes ===
Climate change affects human health adversely and its impact on the skin is no exception. It is one of the greatest threats to our capacity to benefit in the context of “[[Cosmetics|Skin Care]] for All.”<ref name=":2" /> In a study conducted in South Africa, the reduced work capacities and outputs were attributed to heat waves, which caused severe sunburns, sleeplessness, irritability, and exhaustion in workers. [[Risk assessment|Risk assessments]] were conducted for extreme health impacts across African countries, especially Kenya, both at the regional and city scale.<ref name=":1" /> Rising temperature and humidity increase skin bacteria growth overall geographical distribution of other organisms that infect humans. The different organisms that form the skin microflora have variable optimal temperature for survival and growth. ''[[Staphylococcus aureus]]'' and ''[[Corynebacterium striatum|Corynebacterium sp.]]'' amongst others are more tolerant to rising temperatures and higher salt conditions compared to other, non-commensal bacteria.<ref name=":2" />

=== Diarrhea diseases ===
{{See also|Diarrhea}}
One of the most commonly transmitted waterborne disease categories are the diarrhea diseases.<ref name="(Levy et al., 2018)" /> These diseases are transmitted through unsafe drinking water or recreational water contact.<ref name="(Hunter, 2003)" /> Diarrheal diseases account for 10–12% of deaths in children under five, as the second leading cause of death in children this age. They are also the second leading cause of death in low and middle income countries. Diarrhea diseases account for an estimated 1.4–1.9&nbsp;million deaths worldwide.<ref name="(Levy et al., 2016)" />

=== Fungal infections ===
[[Fungal infection|Fungal infections]] will also see an increase due to the warming of certain climates.<ref name="Ostfeld_2009" /> For example, the fungus [[Cryptococcus gattii]] has been found in Canada but is normally found in warmer climates such as in [[Australia (continent)|Australia]]. There are now two [[Strain (biology)|strains]] of this fungus in the northwestern part of North America, affecting many terrestrial animals. The spread of this fungus is hypothesized to be linked to climate change.<ref name="Cooney_2011" />

=== Emergence of new infectious diseases ===
There is concern about the emergence of new diseases from the [[Fungal infection|fungal]] kingdom. Mammals have ''endothermy'' and ''homeothermy'', which allows them to maintain elevated body temperature through life; but it can be defeated if the fungi were to adapt to higher temperatures and survive in the body.<ref>{{cite journal | vauthors = Casadevall A | title = Climate change brings the specter of new infectious diseases | journal = The Journal of Clinical Investigation | volume = 130 | issue = 2 | pages = 553–555 | date = February 2020 | pmid = 31904588 | pmc = 6994111 | doi = 10.1172/JCI135003 }}</ref> Fungi that are pathogenic for insects can be experimentally adapted to replicate at mammalian temperatures through cycles of progressive warming. This demonstrates that fungi are able to adapt rapidly to higher temperatures. The emergence of ''[[Candida auris]]'' on three continents is proposed to be as a result of global warming and has raised the danger that increased warmth by itself will trigger adaptations on certain microbes to make them pathogenic for humans.<ref>{{cite journal | vauthors = Lockhart SR, Etienne KA, Vallabhaneni S, Farooqi J, Chowdhary A, Govender NP, Colombo AL, Calvo B, Cuomo CA, Desjardins CA, Berkow EL, Castanheira M, Magobo RE, Jabeen K, Asghar RJ, Meis JF, Jackson B, Chiller T, Litvintseva AP | display-authors = 6 | title = Simultaneous Emergence of Multidrug-Resistant Candida auris on 3 Continents Confirmed by Whole-Genome Sequencing and Epidemiological Analyses | journal = Clinical Infectious Diseases | volume = 64 | issue = 2 | pages = 134–140 | date = January 2017 | pmid = 27988485 | pmc = 5215215 | doi = 10.1093/cid/ciw691 }}</ref>

It is projected that [[Cross-species transmission|interspecies viral sharing]], that can lead to [[Spillover infection#Spillover zoonoses|novel viral spillovers]], will increase due to ongoing climate change-caused geographic range-shifts of mammals (most importantly [[Bat|bats]]). [[Pandemic prevention|Risk hotspots would mainly be located at]] "high elevations, in biodiversity hotspots, and in areas of high human population density in Asia and Africa".<ref>{{cite journal | vauthors = Carlson CJ, Albery GF, Merow C, Trisos CH, Zipfel CM, Eskew EA, Olival KJ, Ross N, Bansal S | display-authors = 6 | title = Climate change increases cross-species viral transmission risk | journal = Nature | volume = 607 | issue = 7919 | pages = 555–562 | date = July 2022 | pmid = 35483403 | doi = 10.1038/s41586-022-04788-w | bibcode = 2022Natur.607..555C | s2cid = 248430532 | doi-access = free | biorxiv = 10.1101/2020.01.24.918755 }}</ref>

Climate change may also lead to new infectious diseases due to changes in microbial and vector geographic range. Microbes that are harmful to humans can adapt to higher temperatures, which will allow them to build better tolerance against human endothermy defences.<ref>{{cite journal | vauthors = Casadevall A | title = Climate change brings the specter of new infectious diseases | journal = The Journal of Clinical Investigation | volume = 130 | issue = 2 | pages = 553–555 | date = February 2020 | pmid = 31904588 | pmc = 6994111 | doi = 10.1172/JCI135003 }}</ref>

== Infectious diseases in wild animals ==
{{Further|Effects of climate change on biomes}}
Climate change and increasing temperatures will also impact the health of wildlife animals as well. Specifically, climate change will impact wildlife disease, specifically affecting "geographic range and distribution of wildlife diseases, plant and animal phenology, wildlife host-pathogen interactions, and disease patterns in wildlife".<ref name="Hofmeister_2010">{{Cite journal | vauthors = Hofmeister EK, Rogall GM, Wesenberg K, Abbott RC, Work TM, Schuler K, Sleeman JM, Winton J |date=2010 |title=Climate change and wildlife health: direct and indirect effects |journal=Fact Sheet |page=4 |doi=10.3133/fs20103017 |issn=2327-6932 |doi-access=free}}</ref>

The health of wild animals, particularly birds, is assumed to be a better indicator of early climate change effects because very little or no control measures are undertaken to protect them.<ref name="Caminade219" />

=== Geographic range and distribution of wildlife diseases ===
Northern geographic shifts of disease vectors and parasitic disease in the Northern Hemisphere have likely been due to global warming. The geographic range of a lung parasite that impacts ungulates like caribou and mountain goats, ''Parelaphostrongylus odocoilei'', has been shifting northward since 1995, and a tick vector for Lyme disease and other tick-borne zoonotic diseases known as ''[[Ixodes scapularis]]'' has been expanding its presence northward as well. It is also predicted that climate warming will also lead to changes in disease distribution at certain altitudes. At high elevation in the Hawaiian Islands, for example, it is expected that climate warming will allow for year-round transmission of [[avian malaria]]. This increased opportunity for transmission will likely be devastating to endangered native Hawaiian birds at those altitudes that have little or no resistance to the disease.<ref name="Hofmeister_2010" />

=== Phenology and wildlife diseases ===
[[Phenology]] is the study of seasonal cycles, and with climate change the seasonal biologic cycles of many animals have already been affected. For example, the transmission of tick-borne encephalitis (TBE) is higher to humans when early spring temperatures are warmer. The warmer temperatures result in an overlap in feeding activity of ticks who are infected with the virus (nymphal) with ticks who aren't (larval). This overlapped feeding leads to more of the uninfected larval ticks acquiring the infection and therefore increases the risk of humans being infected with TBE. On the other hand, cooler spring temperatures would result in less overlapped feeding activity, and would therefore decrease the risk of zoonotic transmission of TBE.<ref name="Hofmeister_2010" />

=== Wildlife host-to-pathogen interaction ===
The transmission of pathogens can be achieved through either direct contact from a diseased animal to another, or indirectly through a host like infected prey or a vector. Higher temperatures as a result of climate change results in an increased presence of disease producing agents in hosts and vectors, and also increases the "survival of animals that harbor disease".<ref name="Hofmeister_2010" /> Survival of ''[[Parelaphostrongylus tenuis]]'', a brain worm of white-tailed deer that affects moose, could be increased due to the higher temperatures and milder winters that are caused by climate change. In moose, this brain causes neurological disease and eventually ends up being fatal. Moose are already facing heat stress due to climate change, and may have increased susceptibility to parasitic and infectious diseases like the brain worm.<ref name="Hofmeister_2010" />

=== Wildlife disease patterns ===
Predicting the impact climate change might have on disease patterns in different geographic regions can be difficult, because its effects likely have high variability. This has been more evident in marine ecosystems than terrestrial environments, where massive decline in coral reefs has been observed due to disease spread.<ref name="Hofmeister_2010" />

==Infectious diseases in domestic animals and livestock==
Vector-borne diseases seriously affect the health of domestic animals and [[livestock]] (e.g., [[trypanosomiasis]], [[Rift Valley fever|Rift Valley Fever]], and [[Bluetongue disease|bluetongue]]). Therefore, climate change will also indirectly affect the health of humans through its multifaceted impacts on food security, including livestock and plant crops.<ref name="Caminade219" />

Mosquitoes also carry diseases like ''[[Dirofilaria immitis]]'' which affect dogs (dog heartworm). Therefore, [[tropical diseases]] will probably migrate and become [[endemic]] in many other ecosystems due to an increase in mosquito range.<ref>{{cite journal | vauthors = Lacetera N | title = Impact of climate change on animal health and welfare | journal = Animal Frontiers | volume = 9 | issue = 1 | pages = 26–31 | date = January 2019 | pmid = 32002236 | pmc = 6951873 | doi = 10.1093/af/vfy030 | doi-access = free }}</ref>{{excerpt|Effects of climate change on livestock#Pathogens and parasites}}

== Responses ==
The policy implications of climate change and infectious diseases fall into two categories:<ref name="Watts_2015">{{cite journal | vauthors = Watts N, Adger WN, Agnolucci P, Blackstock J, Byass P, Cai W, Chaytor S, Colbourn T, Collins M, Cooper A, Cox PM, Depledge J, Drummond P, Ekins P, Galaz V, Grace D, Graham H, Grubb M, Haines A, Hamilton I, Hunter A, Jiang X, Li M, Kelman I, Liang L, Lott M, Lowe R, Luo Y, Mace G, Maslin M, Nilsson M, Oreszczyn T, Pye S, Quinn T, Svensdotter M, Venevsky S, Warner K, Xu B, Yang J, Yin Y, Yu C, Zhang Q, Gong P, Montgomery H, Costello A | display-authors = 6 | title = Health and climate change: policy responses to protect public health | journal = Lancet | volume = 386 | issue = 10006 | pages = 1861–1914 | date = November 2015 | pmid = 26111439 | doi = 10.1016/S0140-6736(15)60854-6 | hdl-access = free | s2cid = 205979317 | hdl = 10871/17695 }}</ref>
# Enacting policy that will reduce greenhouse gas emissions, thus slowing down climate change, and
# Mitigating problems that have already arisen, and will inevitably continue to develop, due to climate change.

Addressing both of these areas is of importance, as those in the poorest countries face the greatest burden. Additionally, when countries are forced to contend with a disease like malaria (for example), their prospects for economic growth are slowed. This contributes to continued and worsening global inequality.<ref name="Campbell-Lendrum_2015">{{cite journal | vauthors = Campbell-Lendrum D, Manga L, Bagayoko M, Sommerfeld J | title = Climate change and vector-borne diseases: what are the implications for public health research and policy? | journal = Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences | volume = 370 | issue = 1665 | pages = 20130552 | date = April 2015 | pmid = 25688013 | pmc = 4342958 | doi = 10.1098/rstb.2013.0552 }}</ref>

Policies are required that will significantly increase investments in public health in developing countries. This achieves two goals, the first being better outcomes related to diseases like malaria in the affected area, and the second being an overall better health environment for populations.<ref name="Watts_2015" /> It is also important to focus on "[[One Health|one-health]] approaches."<ref name="Watts_2015" /> This means collaborating on an interdisciplinary level, across various geographic areas, to come up with workable solutions. As is the case when responding to the effects of climate change, vulnerable populations including children and the elderly will need to be prioritized by any intervention.

The United Nations Environment Programme states that: "The most fundamental way to protect ourselves from [[Zoonosis|zoonotic diseases]] is to prevent destruction of nature. Where ecosystems are healthy and bio-diverse, they are resilient, adaptable and help to regulate diseases."<ref>{{cite web |date=22 May 2020 |title=Science points to causes of COVID-19 |url=https://www.unenvironment.org/news-and-stories/story/science-points-causes-covid-19 |access-date=2 June 2020 |website=United Nations Environmental Programm |publisher=United Nations}}</ref>

=== Monitoring and research ===
[[File:Anopheles_stephensi.jpeg|thumb|An ''[[Anopheles stephensi]]'' mosquito shortly after obtaining blood from a human (the droplet of blood is expelled as a surplus). This mosquito is a vector of [[malaria]], and mosquito control is an effective way of reducing its incidence.]]
Significant progress has been achieved in terms of surveillance systems, disease and vector control measures, vaccine development, diagnostic tests, and mathematical risk modeling/mapping in recent decades.<ref name="Caminade219" />

A tool that has been used to predict this distribution trend is the Dynamic Mosquito Simulation Process (DyMSiM). DyMSiM uses [[Epidemiology|epidemiological]] and [[Entomology|entomological]] data and practices to model future mosquito distributions based upon climate conditions and mosquitos living in the area.<ref>{{cite journal | vauthors = Butterworth MK, Morin CW, Comrie AC | title = An Analysis of the Potential Impact of Climate Change on Dengue Transmission in the Southeastern United States | journal = Environmental Health Perspectives | volume = 125 | issue = 4 | pages = 579–585 | date = April 2017 | pmid = 27713106 | pmc = 5381975 | doi = 10.1289/EHP218 }}</ref> This modeling technique helps identify the distribution of specific species of mosquito, some of which are more susceptible to viral infection than others.{{citation needed|date=March 2022}}

Scientists are carrying out attribution studies, to find the degree to which climate change affects the spread of infectious diseases. There is also a need for scenario modeling which can help further our understanding of future climate change consequences on infectious disease rates.<ref name="Campbell-Lendrum_2015" /> Surveillance and monitoring of infectious diseases and their vectors is important to better understand these diseases.<ref name="Watts_2015" /> Governments should accurately model changes in vector populations as well as the burden of disease, educate the public on ways to mitigate infection and prepare health systems for the increasing disease load.

== See also ==
* [[Disease ecology]]
* [[Effects of climate change on human health]]
* [[Environmental health]]

== References ==
{{reflist}}

{{Climate change}}
{{Epidemics}}
{{Authority control}}

[[Category:Effects of climate change]]
[[Category:Infectious diseases]]
[[Category:Disease ecology]]
[[Category:Climate change and society]]
[[Category:Waterborne diseases]]
[[Category:Climate change and the environment]]
[[Category:Environment and health]]