Viral eye infections are the most common type of eye infection. Viral conjunctivitis is much more common than bacterial. Among viral infections, a type of virus known as the adenovirus is the most common cause of conjunctivitis. Even herpes-simplex viral eye infections are more common than might be supposed. Viruses like cytomegalovirus retinitis are actually quite widespread, with most people coming into contact with the virus at some point in their lives. Most people, however, never feel any symptoms since their immune systems are strong enough to fight the virus off.