Adenoviral Conjunctivitis (Epidemic Keratoconjunctivitis)

Overview

Adenoviral conjunctivitis is the most common cause of viral conjunctivitis and one of the most common causes of infectious conjunctivitis overall, spanning a clinical spectrum from mild, self-limited follicular conjunctivitis to severe epidemic keratoconjunctivitis (EKC) with corneal involvement and visual morbidity.¹ It is highly contagious and primarily a clinical diagnosis, though laboratory confirmation is increasingly available.²

Epidemiology & Risk Factors

Adenoviral conjunctivitis accounts for a large share of eye-related office and emergency visits, with estimated US incidence as high as 20 million cases per year.² Transmission occurs primarily through hand-to-eye contact, contact with ocular secretions, respiratory droplets, and fomites — including reused ophthalmic instruments and multi-dose eye drop bottles, making healthcare settings themselves a recognized source of outbreaks.³ Multiple adenovirus serotypes exist, and the specific serotype influences the clinical syndrome and severity.²

Pathophysiology

Adenovirus infects conjunctival and corneal epithelial cells, triggering an acute inflammatory follicular response. Certain serotypes (classically within species D) are particularly associated with epithelial keratitis and the delayed formation of subepithelial infiltrates — thought to represent a host immune response to viral antigen deposited in the anterior stroma rather than active ongoing infection at that stage.³ This distinction matters clinically, since infiltrates can persist or recur for months after the acute infectious phase has resolved.

Clinical Presentation

Three recognized clinical patterns exist³:

• Epidemic keratoconjunctivitis (EKC) — the most severe pattern: watery discharge, marked conjunctival hyperemia and chemosis, ipsilateral preauricular lymphadenopathy, and (after several days) punctate epithelial keratitis progressing to subepithelial infiltrates
• Pharyngoconjunctival fever — abrupt fever, pharyngitis, bilateral conjunctivitis, and periauricular lymphadenopathy, more common in children
• Isolated follicular conjunctivitis without corneal or systemic involvement

Symptoms typically begin unilaterally and spread to the fellow eye within days. A prominent follicular reaction, watery discharge, and preauricular adenopathy together are strong clinical clues, though the overall clinical diagnostic accuracy for viral conjunctivitis is under 50%, meaning bacterial and viral conjunctivitis are frequently confused on presentation alone.³

Exam Findings

• Follicular conjunctival reaction (bulbar and palpebral)
• Watery, non-purulent discharge
• Conjunctival hyperemia and chemosis
• Ipsilateral (or bilateral) preauricular lymphadenopathy
• Pseudomembrane or true membrane formation in more severe cases
• Punctate epithelial keratitis in the first 1–2 weeks
• Focal, white, subepithelial infiltrates appearing 1–3 weeks after onset, which may persist for months

Differential Diagnosis

• Bacterial conjunctivitis (typically more purulent discharge, less watery, no preauricular node)
• Allergic conjunctivitis (itching prominent, bilateral, papillary rather than follicular reaction)
• Herpes simplex keratoconjunctivitis (dendritic epithelial lesions, decreased corneal sensation, usually unilateral vesicular lid lesions if primary)
• Chlamydial (inclusion) conjunctivitis in sexually active adults with chronic, unresponsive follicular conjunctivitis
• Toxic or medicamentosa conjunctivitis from chronic topical drop use

Management

Rapid in-office antigen testing can support the clinical diagnosis and reduce unnecessary antibiotic use, though it is not universally used.³ No antiviral therapy is definitively established or universally approved for adenoviral conjunctivitis; management is primarily supportive with artificial tears, cool compresses, and symptomatic relief.² Topical antibiotics are not routinely indicated and should be reserved for suspected bacterial co-infection or high-risk patients (e.g., young children).²

Topical povidone-iodine has emerging evidence as a treatment that may reduce viral load and shorten symptom duration with a favorable side-effect profile, though optimal concentration and dosing protocols are still being refined and it is not yet considered a definitive standard of care.¹ Topical corticosteroids are sometimes used for visually significant subepithelial infiltrates or pseudomembranes but can prolong viral shedding and should be used cautiously and typically with specialist input.

Infection control is a critical component of management given the high contagiousness of adenovirus: strict hand hygiene, avoidance of shared towels/pillows, instrument disinfection between patients, and patient education about the contagious period (which can extend up to two weeks after symptom onset) are essential to prevent outbreaks, including within clinics themselves.³

Complications

• Persistent subepithelial infiltrates causing glare and decreased vision, sometimes for months to years
• Pseudomembrane formation, which if untreated can lead to symblepharon and conjunctival scarring
• Secondary bacterial infection
• Rarely, permanent visual disability from scarring or persistent infiltrates²

Clinical Pearls

• Clinical diagnostic accuracy for viral versus bacterial conjunctivitis is under 50% — maintain a low threshold for point-of-care antigen testing when available³
• Subepithelial infiltrates typically appear 1–3 weeks after onset and can persist for months, well after the contagious period has ended
• No antibiotic is needed for uncomplicated adenoviral conjunctivitis; treatment is supportive
• Warn patients about contagiousness (up to ~2 weeks) and counsel on hand hygiene and avoiding shared personal items
• Clinics themselves can be a source of adenovirus outbreaks via contaminated instruments or multi-dose bottles — strict disinfection protocols matter for staff as much as for patients³

Common Pitfalls

• Prescribing topical antibiotics reflexively for presumed "pink eye" without considering a viral etiology
• Missing pseudomembranes, which require removal (peeling) to prevent symblepharon formation
• Using topical steroids too readily, which can prolong viral shedding and contagiousness
• Failing to counsel patients on contagion precautions, contributing to household or workplace spread
• Assuming persistent blurry vision from subepithelial infiltrates months later is a new or unrelated problem rather than a known sequela