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News|Articles|April 5, 2024

Hong Kong Reports First Human Case of B Virus

The case involves a man who had contact with wild monkeys.

Hong Kong’s Centre for Health Protection announced this week it recorded the area's first human case of B virus, also known as the herpes simiae virus. The serious, but very rare viral infection was diagnosed in a 37-year-old man who had contact with wild monkeys and was wounded by them during a visit to Kam Shan Country Park in late February. The man who was previously in good health was admitted to Yan Chai Hospital through the accident and emergency department on March 21 with a fever and decreased conscious level.1

The man's cerebrospinal fluid specimen tested positive for the B virus by the centre's laboratory. He is receiving treatment at the hospital’s intensive care unit and is in critical condition.1

The health organization is investigating the case, and is warning the public to refrain from touching or feeding wild monkeys to minimize the risk of contracting the virus. In Hong Kong, there is a population of wild monkeys with a total of about 1800 animals. They are distributed in 30 social troops, according to the Agriculture, Fisheries and Conservation Department in Hong Kong.The existing species in the area are the Rhesus Macaque (Macaca mulatta), the Long-tailed Macaque (M. fascicularis) and their hybrids. They are mainly found in Kam Shan, Lion Rock, and Shing Mun Country Parks.1,2

Although this is the first case reported in Hong Kong, the centre said other cases have been reported in other places such as the US, Canada, China. and Japan. These cases were mainly caused by monkey bites or scratches, adding that human-to-human transmission is very rare. It also explained that the B virus is naturally carried in the saliva, urine, and stool of macaques.1

What You Need to Know

The B virus, also known as herpes simiae virus, is a rare but potentially serious viral infection that can affect humans who come into contact with macaque monkeys.

To prevent B virus infection, it's crucial to avoid contact with wild monkeys and refrain from feeding or touching them. In case of exposure, immediate medical attention is necessary.

Health organizations like the Centre for Health Protection in Hong Kong emphasize public awareness and caution regarding the risks associated with wild monkeys.

Symptoms, Incidence Rates, Treatment
An infected person may initially present with flu-like symptoms that may progress to infection of the central nervous system. According to the Centers for Disease Control and Prevention (CDC), symptoms typically start within 1 month of being exposed to a monkey with the B virus infection, but could appear in as little as 3 to 7 days.3

CDC states the B virus was first identified in 1932, and that only 50 people have been documented to have contracted this infection. Of the 50 cases, 21 patients died. The federal agency says many of these patients became infected after they were bitten or scratched by a macaque monkey, or when tissue or fluids from a monkey got on their broken skin, such as by needle stick or cut.3

The virus can spread to the central nervous system (CNS) and cause the following symptoms: hyperesthesias (increase in sensitivity to stimuli); ataxia (lack of voluntary control of muscle movements); diplopia (double vision); agitation; ascending flaccid paralysis (extreme weakness due to reduced muscle tone).3

CDC offers treatment guidance on their site, and they break down treatment, depending on exposure.

For prophylaxis for exposure to B virus:

  • Valacylovir—1g by mouth every eight hours for 14 days, or
  • Acyclovir—800 mg by mouth five times daily for 14 days

For treatment of B virus infection:

With no CNS symptoms

  • Acyclovir—12.5–15 mg/kg intravenously every eight hours, or
  • Ganciclovir—5 mg/kg intravenously every 12 hours

With CNS symptoms

  • Ganciclovir—5 mg/kg intravenously every 12 hoursProphylaxes for exposure to B virus have been shown to effectively protect rabbits from lethal infectious doses of B virus, but no comparable studies of efficacy in humans have been possible.3

The CDC explains that the virus is very rare and that hundred of bites from these animals occur every year at facilities that house monkeys.3

For the general public, the Hong Kong Centre for Health Protection urges people to stay away from wild monkeys and wash any wounds caused by them with running water and seek medical attention immediately.1

References
1. HK logs 1st human B virus case. Centre for Health Protection press release. April 3, 2024. Accessed April 5, 2024. https://www.info.gov.hk/gia/general/202404/03/P2024040400151.htm

2. Wild Monkeys of Hong Kong. Agriculture, Fisheries and Conservation Department. Accessed April 5, 2024.
https://www.afcd.gov.hk/english/conservation/con_fau/con_fau_mon/con_fau_mon_wild/con_fau_mon_wild.html

3. B Virus (herpes B, monkey B virus, herpesvirus simiae, and herpesvirus B) CDC. Last reviewed January 31, 2019. Accessed April 5, 2024. https://www.cdc.gov/herpesbvirus/healthcare-providers.html

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