Viral conjunctivitis is more commonly known as pink eye. Although several different viruses have been known to cause conjunctivitis, by far the most common virus isolated is adenovirus. The most common symptoms of viral conjunctivitis include red eyes with excessive tearing and swelling. Vision in the early stages of adenoviral conjunctivitis is usually unchanged. With more severe viral conjunctivitis, pain and reduced vision can become more prominent. In the most severe cases, patients develop corneal scarring, chronic dry eye, and conjunctival scarring (see cicatrizing conjunctivitis). Patients with viral conjunctivitis usually have a history of sick contacts or an upper respiratory tract infection. Most commonly, symptoms begin unilaterally and then the second eye becomes involved. Patients are highly contagious as long as the eye is infected (on average 7–10 days). Depending on the strain of adenovirus, symptoms can be self-limited or patients can have postinfectious sequelae for months to years following the active infection. Epidemic keratoconjunctivitis has been reported.
Note: Although not a classical viral conjunctivitis, avian influenza A subtype H7 ("poultry flu") can lead to similar symptoms.