What is the most common respiratory virus that causes conjunctivitis?

Adenovirus is the Most Common Respiratory Virus Causing Conjunctivitis

Adenovirus is the most common respiratory virus that causes conjunctivitis, accounting for up to 80% of all viral conjunctivitis cases. 1 This virus is highly contagious and can cause significant ocular complications, particularly in the form of epidemic keratoconjunctivitis (EKC).

Viral Conjunctivitis: Epidemiology and Causative Agents

• Viruses account for approximately 80% of all acute conjunctivitis cases 1
• Among respiratory viruses causing conjunctivitis:
  • Adenovirus is the predominant pathogen (up to 75% of all conjunctivitis cases) 2
  • Other viral causes include:
    • Herpes simplex virus (HSV)
    • Varicella zoster virus (VZV)
    • Enterovirus (less common)

Clinical Presentation of Adenoviral Conjunctivitis

Adenoviral conjunctivitis typically presents with:

• Abrupt onset of symptoms
• Unilateral initially, often becoming sequentially bilateral
• Bulbar conjunctival injection (redness)
• Watery discharge
• Follicular reaction of inferior tarsal conjunctiva
• Chemosis and eyelid swelling
• Possible preauricular lymphadenopathy 3

Forms of Adenoviral Ocular Infection

1. Epidemic Keratoconjunctivitis (EKC):

   • Most severe form of adenoviral conjunctivitis
   • Can lead to subepithelial infiltrates (SEIs) in the cornea
   • May cause long-term visual disability 2

2. Pharyngoconjunctival Fever:

   • Characterized by high fever, pharyngitis, bilateral conjunctivitis
   • Preauricular lymph node enlargement 4

3. Isolated Follicular Conjunctivitis:

   • Without corneal or systemic involvement 4

Diagnosis and Differential Considerations

The clinical accuracy in diagnosing viral conjunctivitis is less than 50% without specific testing 4. Key diagnostic features include:

• Follicular reaction (suggestive of viral etiology)
• Watery discharge (versus purulent discharge in bacterial cases)
• Recent exposure to infected individuals
• Concurrent upper respiratory infection 3

Laboratory testing options:

• Adenovirus nucleic acid amplification test (NAAT)
• Adenovirus culture
• Rapid diagnostic tests can help reduce unnecessary antibiotic use 3, 4

Management Approach

Treatment for adenoviral conjunctivitis is primarily supportive as most cases are self-limited 4:

• Patient education on highly contagious nature
• Strict hand hygiene
• Avoid sharing towels, pillows, or eye drops
• Cool compresses for symptomatic relief
• Artificial tears for lubrication
• Isolation precautions to prevent spread in healthcare settings

Potential Complications

• Subepithelial corneal infiltrates (SEIs)
• Conjunctival scarring
• Symblepharon formation
• Dry eye syndrome
• Corneal scarring in severe cases 3, 2

Prevention of Transmission

Given the high contagiousness of adenoviral conjunctivitis:

• Implement strict hand washing protocols
• Sanitize surfaces and medical instruments
• Avoid touching eyes with unwashed hands
• Isolate affected individuals when possible
• Consider in-office povidone-iodine irrigation in high-risk settings 2

Clinical Pearls

1. Adenoviral conjunctivitis is highly transmissible and can cause outbreaks in schools, workplaces, and healthcare settings
2. The presence of follicles rather than papillae is more characteristic of viral than bacterial conjunctivitis
3. Symptoms typically peak at 3-5 days and resolve within 1-2 weeks, though subepithelial infiltrates may persist longer
4. Corticosteroids should be used cautiously as they may prolong viral shedding and have vision-threatening side effects 5
5. Antibiotics are ineffective against viral conjunctivitis and should be avoided unless bacterial superinfection is suspected

Human adenovirus is not only the most common cause of viral conjunctivitis but can also cause systemic infections including respiratory disease and gastroenteritis, highlighting its importance as a respiratory pathogen with significant ocular manifestations 2.