4.1. Epidemiology and Clinical Relevance
Adenovirus is by far the most common cause of viral conjunctivitis and tends to be the most virulent. Herpes simplex virus (HSV) (usually type 1) primarily causes conjunctivitis in children and usually produces a mild inflammatory response. Other viral pathogens, which can cause viral conjunctivitis in the elderly, include enterovirus, coxsackievirus, and varicella-zoster.
Viral conjunctivitis classically produces a clear watery discharge, a follicular con-junctival reaction, and preauricular lymphadenopathy. A purulent discharge may be seen on occasion but is usually more characteristic of a bacterial conjunctivitis. Con-junctival follicles represent lymphoid germinal follicles within the conjunctiva and appear as translucent cobblestones or pebbles with small blood vessels arborizing over the surface. Follicles are highly characteristic of viral infections, although they can also be seen in chlamydial infections of the conjunctiva. It should also be pointed out that due to the highly contagious nature of viral infections, the majority of patients present with bilateral eye involvement, whereas bacterial conjunctival infections typically present unilaterally.
Epidemic keratoconjunctivitis (EKC) is caused by adenovirus types 8 and 19 and is characterized by severe eye pain, photophobia, diffuse punctate corneal epithelial defects, and conjunctivitis. The inflammatory reaction produced by this viral organism can be so intense that inflammatory membranes or pseudomembranes and subepithelial corneal infiltrates develop. True membranes are differentiated from pseudomembranes by the presence of bleeding on removal of true membranes. The corneal subepithelial infiltrates do not occur in every patient but typically manifest 10-14 d after the onset of symptoms. These infiltrates are sterile and represent an immune reaction to viral antigens. They usually resolve spontaneously without visual sequelae, but it may take several months for complete resolution. During the acute infiltrative phase, patients may experience a temporary reduction in vision.
EKC typically lasts for 2-4 wk with contagious viral shedding occurring during the first 2 wk from the onset of symptoms. Therefore, patients must be quarantined during this infectious period. The virus is extremely contagious and can remain viable on inanimate objects such as equipment, doorknobs, and other fomites for up to 2 mo (2). Adenovirus has also been found to be common cause of severe outbreaks of viral conjunctivitis in chronic care facilities (3).
The diagnosis of viral conjunctivitis is generally made on clinical findings; however, culture and sensitivity testing does prove useful in identifying cases of EKC and excluding a concurrent bacterial conjunctivitis.
As with all forms of viral conjunctivitis, there is no specific treatment for adenoviral conjunctivitis. Thus, therapy is aimed at palliation and limiting complications. The use of cool compresses, artificial tears, and analgesics are typically very helpful in easing patients' discomfort. Antibiotics are not indicated, unless the patient develops signs of a superimposed bacterial infection. Topical corticosteroids should be avoided.
Hand-to-eye contamination is the primary route of transmission of viral conjunctivitis. Thus, precautions regarding hand-to-eye contact and handwashing should be adhered to regarding this condition. As stated earlier, it is also important to note that adenovirus types 8 and 19 remain infectious for up to 2 mo after being deposited on environmental surfaces (2,4). Therefore, contracting EKC does not require direct contact with an infected individual.
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