Herpes B virus is also known as Cercopithecine herpesvirus 1, herpesvirus simiae, B virus, and Macacine herpesvirus 1. The term "B virus" will be used in this discussion. Infection typically causes an asymptomatic herpes simplex virus-like infection in its natural primate host, Asian macaques. Transmission of B virus to humans can result in a fatal encephalomyelitis.

All species of macaques may carry B virus, including colonies exported from Asia to other parts of the world and those in zoos or research facilities. The virus has been most commonly isolated from rhesus macaques (Macaca mulatta) and cynomolgus monkeys (Macaca fascicularis). Other infected species include the pig-tailed macaque (Macaca nemestrina), bonnet macaque (Macaca radiata), Japanese macaque (Macaca fuscata), stump-tailed macaque (Macaca arctoides), and Taiwan macaque (Macaca cyclopis).

Animals spread B virus through oral and genital secretions. The virus can be stored in sensory ganglia and reactivate in monkeys, resulting in viral shedding. Humans are infected when exposed to oral, genital, or ocular secretions from an infected monkey, usually via a bite or scratch. Humans have also been infected when exposed to infected tissue and infected fomites (eg, needlestick or cages). Inhalation of aerosolized infected material can lead to infection. Human-to-human transmission due to direct contact of a monkey bite wound from the index patient has been reported. Non-macaque monkeys can acquire B virus from macaques if housed in close proximity and can develop symptomatic disease that is transmissible to humans.

Herpes B virus infection in humans is uncommon, with only several dozen cases reported since 1933. The incubation period for B virus in humans typically ranges from several days to 5 weeks after exposure. Reactivation of disease, years after monkey exposure, has occurred.

Several clinical manifestations of B virus have been described in humans and can overlap with each other. 1) Vesicular or ulcerative lesions at the site of exposure, pain, and regional lymphadenopathy. 2) Flu-like illness consisting of fever, headache, and myalgias followed by neurologic symptoms of numbness, paresthesias, and central nervous system (CNS) symptoms. 3) CNS symptoms vary with the region of brain or spinal cord that is affected but include headache, cranial nerve abnormalities, meningoencephalitis, ascending flaccid paralysis, hyperesthesias, coma, seizures, dysarthria, and dysphagia. Asymptomatic infection with herpes B virus has not been proven to occur. Death follows CNS infection, usually from respiratory failure due to ascending paralysis.

Persons with the highest risk for B virus infection include veterinarians and biomedical laboratory workers who have contact with macaques, and those who work with monkey cell cultures.