B virus

Infectious Agent

Macacine herpesvirus I , or B virus, is an enveloped, double-stranded DNA virus in the family Herpesviridae, genus Simplexvirus . B virus is also commonly referred to as herpes B, monkey B virus, herpesvirus simiae, and herpesvirus B. B virus is commonly found among macaques, a genus of Old World monkeys.


Transmission is typically caused by bites or scratches from an infected macaque but may also occur through contact with body fluids or tissues of an infected macaque. A single case of human-to-human spread has been documented, in which a woman became infected through direct contact with the lesions of her infected spouse.


Macaques are the natural reservoir for B virus infection. No other primates are known to carry any risk of B virus infection unless they have become infected by contact with infected macaques. Although B virus infections in macaques are usually asymptomatic or cause only mild disease, approximately 70% of untreated infections in humans are fatal. People at risk for B virus infection are veterinarians, laboratory workers, and others who have close contact with Old World macaques or monkey cell cultures, but infections in humans are rare. Since B virus was identified in 1932, fewer than 50 cases of human infection have been documented.

Clinical Presentation

Disease onset typically occurs within 1 month of exposure, although the actual incubation period can be as short as 3–7 days. The first signs of disease typically include influenzalike symptoms (fever, headache, myalgias) and sometimes vesicular lesions near the exposure site. Localized neurologic symptoms such as pain, numbness, or itching may occur near the wound site. Lymphadenitis, lymphangitis, nausea, vomiting, and abdominal pain may also occur. Spread of the infection to the central nervous system (CNS) causes acute ascending encephalomyelitis. Most patients with CNS involvement die despite antiviral therapy and supportive care, and those who survive usually suffer serious neurologic sequelae. Respiratory failure associated with ascending paralysis is the most common cause of death.


In the United States, diagnostic testing of human specimens is performed only at the National B Virus Resource Center at Georgia State University. Detection of viral DNA by B virus PCR from clinical specimens is the standard for diagnosis of infection. Detection of B virus–specific antibodies in serum is also diagnostic. Culture is generally unsuccessful as the virus is unlikely to remain viable during transit or after being frozen and thawed. For more information, see www2.gsu.edu/~wwwvir/index.html.


For any suspected exposure, immediate first aid is crucial. The wound should be cleansed by thoroughly washing and scrubbing the area with soap, concentrated detergent solution, povidone-iodine, or chlorhexidine and water. The wound should then be irrigated with running water for 15–20 minutes. For urine splashes to the eyes, repeated flushes of the eyes should be performed for 15 minutes with sterile saline solution or water. Specimens for diagnostic testing should not be obtained from wound sites before washing because doing so may force virus more deeply into the wound.

Antiviral therapy is recommended as postexposure prophylaxis in high-risk exposures (see www.cdc.gov/herpesbvirus/firstaid-treatment.html). When recommended, the first choice of drug for postexposure prophylaxis is valacyclovir and an alternative is acyclovir. If B virus infection is diagnosed, treatment consists of intravenous acyclovir or ganciclovir, depending on whether CNS symptoms are present.


Adhering to laboratory and animal facility protocols will reduce the risk of B virus transmission among laboratory workers. Visitors to parks and other tourist destinations (such as certain religious temples) with free-roaming macaques should avoid contact with the animals (including feeding or petting them).

CDC website: www.cdc.gov/herpesbvirus


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D. Scott Schmid