Source: DownToEarth

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Context

• The recent case of a 37-year-old man in Hong Kong who contracted B virus after being wounded by a wild monkey highlights the potential dangers associated with zoonotic infections.

Details

Background

• B virus, also known as herpes virus B, was first identified in 1932 when a young doctor, William Brebner, was bitten by a macaque monkey during research on poliovirus.
• Since then, there have been 50 recorded cases of human infection, with 21 resulting in fatalities.
• B virus belongs to the herpes family and is classified as a biosafety category 4 virus, the highest level of biosafety rating.
• Prompt treatment with antiviral drugs can be life-saving, but without treatment, the mortality rate can be as high as 70%.
• There is currently no vaccine available for B virus.
• Macaque monkeys are distributed widely across Asia and have been introduced to other regions.
• Despite their close contact with humans in various settings, there are relatively few recorded instances of B virus transmission outside of laboratory settings.

About B virus

• B virus, also known as Cercopithecine herpesvirus 1 (CeHV-1), is a zoonotic virus that primarily infects macaque monkeys, especially those of the genus Macaca, including rhesus macaques (Macaca mulatta) and pig-tailed macaques (Macaca nemestrina).
• While it typically causes asymptomatic or mild infections in its natural hosts, it can be potentially fatal when transmitted to humans.

Virology and Classification:

• B virus is a double-stranded DNA virus classified within the genus Simplexvirus of the subfamily Alphaherpesvirinae.
• Its genome encodes for various proteins involved in viral replication, immune evasion, and pathogenesis.
• B virus shares similarities with herpes simplex virus (HSV), particularly HSV-1, but exhibits distinct pathogenic characteristics.

Natural Hosts:

• B virus primarily infects macaque monkeys, particularly rhesus macaques and pig-tailed macaques.
• In macaques, B virus infections are often asymptomatic or cause only mild symptoms.

Transmission to Humans:

• Human infections with B virus are rare but can occur through direct contact with bodily fluids or tissues of infected macaques.
• Occupational exposure, such as through bites, scratches, or mucosal exposure to macaque fluids, poses the greatest risk to humans.
• The virus can also be transmitted through contaminated surfaces or equipment.

Clinical Presentation in Humans:

• B virus infection in humans, known as B virus disease or herpes B virus encephalitis, can result in severe neurological symptoms.
• Initial symptoms may resemble flu-like illness, including fever, headache, and malaise.
• As the infection progresses, it can lead to neurological complications such as encephalitis, meningoencephalitis, and ascending paralysis.

Diagnosis:

• Diagnosis of B virus infection in humans typically involves clinical evaluation along with laboratory tests.
• Polymerase chain reaction (PCR) assays are used to detect viral DNA in clinical samples, such as swabs from lesions or cerebrospinal fluid.
• Serological tests, including enzyme-linked immunosorbent assay (ELISA) and Western blot, can detect antibodies against B virus.

Treatment:

• There is no specific antiviral therapy approved for B virus infection in humans.
• Treatment primarily involves supportive care and management of symptoms.
• Antiviral drugs such as acyclovir and ganciclovir may be used empirically, although their efficacy against B virus is not well established.

Sources:

DownToEarth

PRACTICE QUESTION Q.  Which of the following statements about B virus is correct? A) B virus primarily infects humans and rarely affects macaque monkeys. B) B virus belongs to the Filoviridae family and is closely related to Ebola virus. C) B virus is transmitted to humans primarily through mosquito bites. D) B virus, also known as herpes virus B, primarily infects macaque monkeys and poses a risk to humans in laboratory settings. Correct Answer: D