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Salem Health: Infectious Diseases & Conditions, 2nd Edition

Monkey B virus

by Anita P. Kuan, , Ph.D.

Category: Diseases and conditions

Anatomy or system affected: nervous system

Also known as: B virus, herpes B, herpesvirus simiae, herpesvirus B, Macacine alphaherpesvirus 1 (formerly Cercopithecine herpesvirus 1)

Monkey B virus is a type of herpesvirus. The virus is carried by the majority of adult macaque monkeys, including rhesus macaques, pig-tailed macaques, and cynomolgus monkeys (also known as crab-eating macaques). Infections in humans are extremely rare, but are often fatal.

Two rhesus monkeys in northern India as photographed by a CDC employee in 1974. The Macaca mulatta is a natural reservoir for Macacine herpesvirus 1, or Monkey B virus. Image courtesy of the CDC. Photo by Dr. Roger Broderson via Public Health Image Library.

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Definition

B virus is a macaque monkey alpha-herpesvirus (Macacine alphaherpesvirus 1) that is similar to the herpes simplex viruses of humans. B virus is not a serious problem in macaques as infected macaques usually have no or only mild symptoms. Transmission of B virus to humans (zoonosis) is exceedingly rare. Only 50 cases of infection have been documented since its identification in 1932, all of which occurred in North America and involved contact with macaques in research facilities. The last documented case occurred in 2008; the previous one in 1997. B virus infection in humans may be rare but, if untreated it has a mortality rate of approximately 80%.

Causes

Infection with B virus in humans is caused by infected animal bites or scratches, or by exposure of mucous membranes, such as the eye, to body fluid or tissue from infected animals.

Risk Factors

Macaque monkeys are widely used as animal models for biomedical research. Working with macaque monkeys, particularly in a research setting, or working with monkey tissue or cell cultures are major risk factors for infection with B virus.

Macaques are widespread throughout Asia (including free-ranging, pet, urban, and temple macaques) and breeding facilities have operated in Asia for decades. B virus-positive macaques and humans have frequent close interactions, yet there are no reported cases of B virus infection in Asia. The reason for this geographic restriction of zoonotic B virus remains unclear.

Symptoms

The clinical course of B virus infection in humans can vary widely. Initial symptoms of infection generally develop one to three weeks after exposure, although they can develop considerably later. Additionally, disease progression and symptoms can vary among individuals, including flu-like symptoms (such as fever and chills, muscle ache, fatigue, and headache), herpetic lesions at the injury site, and symptoms associated with infection of the peripheral or central nervous systems. The virus usually spreads along nerves to the spinal cord and brain. Encephalomyelitis, an inflammation of the brain and spinal cord, develops in the terminal stages of infection. Encephalomyelitis leads to paralysis and often death, typically due to respiratory failure. Individuals surviving B virus infection usually have permanent neurologic damage.

Screening and Diagnosis

Samples from both the exposed human, and when possible the source animal, should be sent for B virus diagnostic testing. Direct culture of B virus is the standard for diagnosis of infection. A quantitative PCR method has been developed and is currently being evaluated for use in clinical diagnosis.

Treatment and Therapy

The first action after suspected exposure to B virus is to rapidly and thoroughly cleanse the wound or exposure site. This can inactivate and wash away virus present in the exposure site. Medical attention should then be sought immediately. Effective treatment with the antiviral medication acyclovir (Valtrex) is dependent on early diagnosis and treatment.

No vaccines are available for B virus.

Prevention and Outcomes

Early diagnosis of infection and subsequent treatment are critical to survival. Once B virus reaches the brainstem, the outcome is almost always death.

The majority of cases involve people working with macaque monkeys. When working with macaque monkeys, every animal should be considered a potential source of B virus and use of proper protective equipment and care should be taken when handling them. Additionally, mucosal exposure to potential sources of B virus should be limited whenever possible.

Further Reading

1 

Eberle, R., & Jones-Engel, L. “Questioning the Extreme Neurovirulence of Monkey B Virus (Macacine alphaherpesvirus 1)” Adv Virol (2018) 5248420. Available at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5831965/

2 

Anderson, C.J. “Population estimate and management options for introduced rhesus macaques” Jour Wild Mgmt (2018) Oct 26, doi:10.1002/jwmg.21588

3 

Elmore, D., & Eberle, R. “Monkey B virus (Cercopithecine herpesvirus 1)” Comp med (2008) 58(1), 11-21.

4 

Hilliard, J. “Monkey B virus.” In: Human Herpesviruses: Biology, Therapy, and Immunoprophylaxis Chapter 57. eds., Arvin, A., et al. Cambridge: Cambridge University Press, 2007. Available at https://www.ncbi.nlm.nih.gov/books/NBK47426/

5 

Huff, J.L. and Barry, P.A. “B-Virus (Cercopithecine herpesvirus 1) Infection in Humans and Macaques: Potential for Zoonotic Disease” Emerg Infect Dis (2003) Feb; 9(2): 246–250

Web Sites of Interest

Centers for Disease Control and Prevention

https://www.cdc.gov/herpesbvirus/index.html

National Organization for Rare Disorders

https://rarediseases.org/rare-diseases/simian-b-virus-infection/

See also: Antiviral drugs: Types; Genital herpes; Herpesviridae; Herpesvirus infections; Immune response to viral infections; Prevention of viral infections; Primates and infectious disease; Treatment of viral infections; Tropical medicine; Viral infections; Viruses: Structure and life cycle; Viruses: Types; Zoonotic diseases.

Citation Types

Type
Format
MLA 9th
Kuan, Anita P. "Monkey B Virus." Salem Health: Infectious Diseases & Conditions, 2nd Edition, edited by H. Bradford Hawley, Salem Press, 2020. Salem Online, online.salempress.com/articleDetails.do?articleName=Infect2e_0366.
APA 7th
Kuan, A. P. (2020). Monkey B virus. In H. B. Hawley (Ed.), Salem Health: Infectious Diseases & Conditions, 2nd Edition. Salem Press. online.salempress.com.
CMOS 17th
Kuan, Anita P. "Monkey B Virus." Edited by H. Bradford Hawley. Salem Health: Infectious Diseases & Conditions, 2nd Edition. Hackensack: Salem Press, 2020. Accessed September 16, 2025. online.salempress.com.