B Virus naturally occurs in macaque monkeys. While relatively benign in its natural host, the alphaherpesvirus can cause rapidly ascending encephalomyelitis with a fatality rate of approximately 80% if spread to humans (through bites, scratches, splashes, or needle-stick injuries). B virus directly affects the central nervous system of infected humans and nonhuman primates. Test sent to Mayo Medical Laboratories; performed by National B Virus Center, Atlanta, GA.