What is the Difference Between Bacterial and Viral Conjunctivitis

Bacterial and viral conjunctivitis are two types of conjunctivitis. Conjunctivitis is also known as pink eye. It is an eye infection that may occur due to a virus, bacteria, or allergens. Viral and bacterial pink eye are highly contagious and sometimes may look similar. However, they are different conditions.

The key difference between bacterial and viral conjunctivitis is their cause. Bacterial conjunctivitis is mainly caused by pathogens such as Staphylococcus aureus, Streptococcus pneumoniae, or Haemophilus influenzae, while viral conjunctivitis is mainly caused by viruses such as adenovirus, herpes simplex virus, picornavirus, coxsackievirus or coronavirus.

1. Overview and Key Difference
2. What is Bacterial Conjunctivitis
3. What is Viral Conjunctivitis
4. Similarities – Bacterial and Viral Conjunctivitis
5. Bacterial vs Viral Conjunctivitis in Tabular Form
6. Summary – Bacterial vs Viral Conjunctivitis
7. FAQ – Bacterial and Viral Conjunctivitis

What is Bacterial Conjunctivitis?

Bacterial conjunctivitis is caused by bacteria. Some of the more common types of bacteria that cause conjunctivitis are Staphylococcus aureus, Streptococcus pneumoniae, and Haemophilus influenzae. Bacterial conjunctivitis usually results in a thick discharge of pus. Other symptoms of bacterial conjunctivitis are similar to viral conjunctivitis.

Figure 01: Bacterial Conjunctivitis

Bacterial pink eye normally develops when people get an ear infection. The risk factors for bacterial pink eye are not washing hands before touching the eyes, using contaminated eye makeup or face creams, sharing makeup, and not cleaning contact lenses before wearing them.

A doctor might prescribe antibiotics to treat bacterial pink eye. However, it is not necessary to have them. This is because bacterial pink eye generally gets better within 2 to 5 days.

What is Viral Conjunctivitis?

Viral conjunctivitis is caused by viruses. Viral conjunctivitis can be contracted if people have a cold or upper respiratory infection. Several viruses can lead to conjunctivitis, such as adenovirus, herpes simplex virus, picornavirus, coxsackievirus, or coronavirus. However, adenoviruses cause up to 90% of viral conjunctivitis cases. Moreover, viral conjunctivitis usually causes watery discharge. It starts in one eye and then moves to the other eye.

Figure 02: Viral Conjunctivitis

The risk factors for viral pink eye may include being around someone who coughs or sneezes while having a respiratory infection. Furthermore, viral conjunctivitis should get better on their own, so there’s no need for any additional treatments.

Similarities Between Bacterial and Viral Conjunctivitis

Bacterial and viral conjunctivitis are two different types of conjunctivitis.
Both of these have similar symptoms, such as the whites of the eye appearing red, swelling of the eyelid, crusty eyelid, watering of the eye, discharge from the eye, itchiness, eye irritation, feeling like something in the eye, etc.
Both these are usually caused by pre-existing conditions.
These normally do not need any treatments.

Difference Between Bacterial and Viral Conjunctivitis

Definition

Bacteria conjunctivitis is a type of conjunctivitis caused by some bacteria.
Viral conjunctivitis is a type of conjunctivitis caused by some viruses.

Causative Agents

Bacteria conjunctivitis is caused by Staphylococcus aureus, Streptococcus pneumoniae, or Haemophilus influenzae.
Viral conjunctivitis is caused by viruses such as adenovirus, herpes simplex virus, picornavirus, coxsackievirus or coronavirus.

Specific Symptoms

The specific symptoms of bacterial conjunctivitis include a thick discharge of pus and the sticking of eyelids together.
The specific symptoms of viral conjunctivitis include watery discharge and starting in one eye and moving to the other eye.

Contagious Period

Bacterial conjunctivitis is contagious from symptom onset until 24 hours after starting antibiotics.
Viral conjunctivitis is contagious before symptoms appear.

Treatment

Bacterial conjunctivitis generally gets better within 2 to 5 days, but doctors may prescribe antibiotics.
There is no need for treatment, and viral conjunctivitis can take up to 3 weeks to completely clear up.

The following table summarizes the difference between bacterial and viral conjunctivitis.

Summary – Bacterial vs Viral Conjunctivitis

Conjunctivitis, pink eye, or Madras eye is an eye condition caused by infection or allergies. Bacterial and viral conjunctivitis are two types of conjunctivitis. Viral conjunctivitis is the most common type of conjunctivitis compared to bacterial conjunctivitis. Bacterial conjunctivitis is mainly caused by pathogens such as Staphylococcus aureus, Streptococcus pneumoniae, or Haemophilus influenzae, while viral conjunctivitis is mainly caused by viruses such as adenovirus, herpes simplex virus, picornavirus, coxsackievirus or coronavirus. This is the summary of the difference between bacterial and viral conjunctivitis.

FAQ: Bacterial and Viral Conjunctivitis

1. How long is bacterial conjunctivitis contagious?

Bacterial conjunctivitis can spread to others as soon as symptoms appear or until 24 hours after antibiotics are started. However, conjunctivitis, which is caused by a virus, is generally contagious before the symptoms appear.

2. How long to use antibiotic eye drops for conjunctivitis?

Adults and children can use topical antibiotics such as tobramycin, trimethoprim/polymyxin B, a fluoroquinolone or chloramphenicol four times daily for 5–7 days. Moreover, patients should be seen every 2–3 days until signs and symptoms are resolved.

3. How to tell if pink eye is viral or bacterial?

Bacterial conjunctivitis usually causes a yellow or green sticky discharge throughout the day which will feel itchy, and the eyelids may become swollen. On the other hand, viral conjunctivitis normally causes a watery discharge during the day and present with sticky discharge in the morning. Moreover, the eye lids are swollen very little in case of viral conjunctivitis.

4. What eye drops are good for viral conjunctivitis?

Topical antihistamine eye drops available for viral conjunctivitis at the drug store are Pataday, Zaditor, or Visine-A. These may work to provide relief from symptoms of viral conjunctivitis.

5. What can cause allergic conjunctivitis?

Exposure to pollen, grass, and other airborne allergens can cause seasonal allergic conjunctivitis, whereas perennial allergic conjunctivitis is generally triggered by indoor allergens such as animal dander, dust, and mold spores.

Reference:

1. “Pink Eye (Conjunctivitis).” Mayo Clinic, Mayo Foundation for Medical Education and Research.
2. Ingrid U Scott, MD. “Viral Conjunctivitis (Pink Eye).” Practice Essentials, Background, Etiology, Medscape.

Image Courtesy:

1. “Bacterial conjunctivitis” By Community Eye (CC BY-NC 2.0) via Flickr
2. “Viral conjunctivitis” By Microrao – Own work (CC BY-SA 4.0) via Commons Wikimedia

CONTENTS

What is Bacterial Conjunctivitis?

What is Viral Conjunctivitis?

Similarities Between Bacterial and Viral Conjunctivitis