B virus case: What we know about ‘monkey virus’ after a man in Hong Kong infected

B virus case: What we know about ‘monkey virus’ after a man in Hong Kong infected

A rare human case of B virus, also known as herpes B or “monkey virus,” has been confirmed in Hong Kong, according to local health authorities.

The Centre for Health Protection (CHP) in the territory confirmed that a 37-year-old male “with good past health” was initially admitted to Yan Chai Hospital’s accident and emergency ward on March 21 to treat a “fever and decreased conscious level”.

But he subsequently reached a critical condition and was transferred to the Intensive Care Unit where he was receiving treatment when the CHP last communicated about the case on April 5.

The man was reported to be wounded by wild monkeys at Hong Kong’s Kam Shan Country Park, a panoramic hilltop also known as Monkey Hill, in late February.

Tests carried out by the CHP determined the patient is suffering from B virus.

Here’s what we know about the virus.

What is B virus?

Also known as herpes simiae virus, B virus is found in macaque monkeys and is a zoonotic disease - transmitted from animals to humans - like rabies or Trichinella.

In simple terms, B virus is the monkey version of human herpes: about 70 per cent of macaques carry the virus, some get sores similar to human herpes and others don’t ever show symptoms at all.

But that’s where the comparison ends, because outside of its natural host, B virus is deadly not only to other species such as chimpanzees but also to humans.

The virus is found in the saliva, urine, and stools of infected macaque monkeys, with bites or scratches capable of causing animal to human transmission, according to the United States’ Centers for Disease Control and Prevention (CDC).

The virus can also be contracted by getting infected monkey tissue onto broken skin or in one’s eyes, nose, or mouth, using a contaminated syringe, getting scratched or cut by a contaminated surface such as a cage, or being exposed to the brain, spinal cord or skull of an infected monkey.

“In 1997, a researcher died from B virus infection after bodily fluid from an infected monkey splashed into her eye,” according to the CDC.

But B virus in humans remains extremely rare, with 50 reported cases - of which 21 fatal - since discovery in 1932. What’s more, only one case of human-to-human infection has been documented, according to the CDC.

“Most people will not come in contact with monkeys, so their risk of getting infected with B virus is very low,” it stated, specifying that those working with animals such as veterinarians or lab workers are at higher risk.

What are B virus symptoms?

If you’ve been in contact with macaques or surfaces infected by them, authorities recommend watching out for symptoms up to a month after being exposed.

Signs resemble flu-like symptoms and include fever and chills, muscle ache, fatigue, and headache, with skin lesions or sores, shortness of breath, nausea, abdominal pain, and hiccups.

“It may be possible for people to have mild B virus infection or no symptoms. However, there are no studies or evidence of this,” says the CDC.

Early diagnosis is essential to avoid the progression of the virus into the central nervous system which can cause encephalitis - inflammation of the brain and spinal cord.

This in turn can lead to permanent neurological damage, problems with muscle coordination, and in some cases, death.

How to detect and treat B virus symptoms?

First aid treatment is recommended in case of exposure. Authorities recommend thoroughly washing the area that was in contact or wounded with soap for about 15 minutes and rinsing it with water for another 15 minutes. Medical assistance should also be sought.

Samples tested with polymerase chain reaction (PCR) test can detect the presence of B virus in humans.

However, the CDC recommends against carrying testing out during exposure as “the act of collection could push infectious virus more deeply into the wound”.

There is no vaccine to protect against B virus but treatment with antiviral medication - such as Aciclovir used to treat herpes in humans - can help and are prescribed on a case-by-case basis.

Hong Kong’s CHP declared epidemiological investigations were “ongoing” and advised people to stay away from wild monkeys and refrain from feeding them.

Local authorities have added B virus infection to their register of “Other communicable diseases of topical public health concern” on which other diseases such as cryptosporidiosis, diarrhoea caused by ingesting parasite infected food or water, are also listed.

This is the first monkey virus infection reported in Hong Kong, but cases have previously been reported in the US, where the disease was discovered, in Japan in 2019 and in mainland China in 2021.