Hsiung, G. D. (VA Hospital, West Haven, Conn. 06516), L S. Kaplow and J. Booss. Herpesvirus infection of guinea pigs. I. Isolation, characterization and pathogenicity. Amer J Epidem 93: 298–307, 1971.—In a survey study of over 200 guinea pigs of five different strains obtained from various sources, over 90% of strain 2 and 35% of muta strain guinea pigs showed a herpes-like virus infection. Isolation of the virus from infected animals required cultivation or co-cultivation of tissue cells. The virus was found to have a relatively narrow host range. Extensive cytopathic effect and high titer of virus yield were obtained in guinea pig and rabbit cell cultures. Primary cell cultures derived from other animal species including man, monkey, hamster and mouse as well as embryonated chicken eggs showed no cytopathic effect with this virus and virus titers, if any, were low. Virus was found widely distributed in the various tissues and organs as well as in white blood cells of infected animals in the presence of circulating neutralizing antibody. Non-strain 2 guinea pigs, including Hartley and FS, can be easily infected experimentally with the guinea pig herpes-like virus (GPHLV) isolated from strain 2 animals. Virus persisted in the white blood cells and tissues of inoculated guinea pigs for as long as 10 months without any evidence of clinical disease.