Herpes simplex keratitis.

Avirulent strains of herpes simplex type 1 (HSV-1) infect and shed and colonize the ganglia in rabbits. This primary infection reduces the severity of subsequent infection by virulent virus and prevents ganglionic colonization by even very virulent neurotropic virus. Only a small proportion of the human population known to be infected with HSV-1 develops clinical disease. It is possible that the severity and likelihood of recurrence of this disease is determined by the virulence of the original infecting HSV-1 strain. In addition, there is evidence for differences in antigenicity among the various virus strains, and it may be that the development of stromal disease is related to the host response to these differences. Among the drugs generally available for the treatment of herpetic disease, trifluridine is currently the newest and most effective. Other compounds, such as acyclovir and BVDU, are being developed; because these drugs are specific for the virus and do not interfere with the metabolic processes of normal cells, they have a very low toxicity. Also, it may be that these compounds have a combined effect with other antiviral agents, such as vidarabine, increasing their potency against stromal disease and iritis.