Author(s): Ludmila Perelygina

Infectious Agent

B virus (Macacine herpesvirus 1) 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 B, and herpesvirus simiae. B virus is commonly found among macaques, a genus of Old World monkeys.

Transmission

B virus is typically transmitted to humans through bites or scratches from an infected macaque, but also can occur through contact with body fluids or tissues of an infected macaque. A single case of human-to-human transmission has been documented, in which a woman became infected through direct contact with lesions on her infected spouse.

Epidemiology

Macaques are the natural reservoir for B virus. No other primates are known to carry B virus unless they become infected through contact with infected macaques. Although B virus infections in macaques are usually asymptomatic or cause only mild disease, ≈70% of untreated infections in humans are fatal.

Infections in humans are rare. Since B virus was identified in 1932, <50 cases of human infection have been documented. People at greatest risk for B virus infection are laboratory workers, veterinarians, and others who have close contact with macaques or macaque cell cultures. International travelers visiting temples and parks with exotic animal life often come in direct contact with free-roaming macaques, which often carry B virus. Children are more likely to be bitten than adults. Although transmission of B virus from macaques to humans in public settings has not been documented, the potential risk for transmission exists.

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 influenza-like symptoms (fever, headache, myalgia) and sometimes vesicular lesions near the exposure site. Localized neurologic symptoms (e.g., pain, numbness, itching) might occur near the wound site. Lymphadenitis, lymphangitis, nausea, vomiting, and abdominal pain also can 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. People who survive usually suffer serious neurologic sequelae. Respiratory failure associated with ascending paralysis is the most common cause of death.

Diagnosis

Before collecting clinical specimens for diagnostic testing, cleanse all wound sites thoroughly (see First Aid & Treatment, next). Obtaining specimens from wound sites before proper cleansing could force virus more deeply into exposed tissue.

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.

Detection of B virus–specific antibodies in serum is also diagnostic. Collect and submit a baseline serum sample as close as possible to the time of injury, and again 14–21 days post-injury for serological testing to evaluate for B virus infection. Testing paired specimens is essential for a reliable diagnosis. Viral culture is generally unsuccessful because the virus is unlikely to remain viable during transit or after being frozen and thawed. For more information on specimen collection, storage, and shipment, see National B Virus Resource Center.

First Aid & Treatment

For suspected exposure, travelers should administer immediate first aid. Travelers should cleanse wounds by thoroughly washing and scrubbing the area with soap, concentrated detergent solution, povidone iodine, or chlorhexidine and water, then irrigate the area with running water for 15–20 minutes. For urine splashes to the eyes, travelers should perform repeated eye flushes for several minutes.

Antiviral therapy is recommended as postexposure prophylaxis in high-risk exposures. When recommended, the drug of choice is valacyclovir, and an alternative is acyclovir. If B virus infection is diagnosed, initiate treatment with intravenous acyclovir or ganciclovir, depending on whether CNS symptoms are present.

Prevention

No vaccine is available for B virus. Laboratories should adhere to laboratory and animal facility protocols to reduce the risk for B virus transmission among workers. Visitors to parks and tourist destinations with free-roaming macaques should avoid feeding or petting the animals, and seek care for possible postexposure prophylaxis if a high-risk exposure occurs. Immediate cleaning of bite and scratch wounds is of utmost importance for disease prevention. Consider postexposure antiviral prophylaxis for high-risk exposures, including any deep bites, and scratches or other wounds to the head, neck, or torso. Contact a medical expert familiar with B virus infections at the earliest opportunity.

CDC website: B virus