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Elizabeth Cheung

Hong Kong reported its first human case of the deadly B virus on Wednesday, with the patient, a 37-year-old man, in a critical condition in hospital after a monkey attack.
The Post looks into the virus, which rarely infects people, and how you can protect yourself against the infection.
1. What is B virus and is it fatal?
The B virus, also known as the human simiae virus, usually spreads from macaque monkeys to people. Macaques are easily infected but usually develop no symptoms or mild ones. The virus can also remain dormant in a macaque’s body.
According to the US Centres for Disease Control and Prevention (CDC), the virus can however be lethal in other primates including chimpanzees and capuchin monkeys.
Infections in people are rare. Since the virus was discovered in 1932, about 50 human infections have been recorded, with 21 deaths.
Past studies show that the mortality rate for people with the viral infection can be as high as 70 to 80 per cent without timely treatment.
Hong Kong’s first human case of B virus fighting for his life after monkey attack
2. How is B virus spread from macaques to humans?
The virus can be found in the saliva, urine and stool of infected macaque monkeys. Humans can get the virus if they are bitten or scratched by an infected monkey.
Infected macaques do not usually spread the B virus, according to CDC information. Only those with weak immunity or who are stressed, and those with blisters on their skin, are more likely to excrete the virus.
Laboratory workers, veterinary surgeons or others who are exposed to monkeys or their specimens have a higher risk of getting the viral infection. They may become infected if they are scratched or get a cut by a contaminated cage or sharp-edged surface, or are exposed to the brain, spinal cord or skull of an infected monkey.
Dr Ho Pak-leung, a clinical associate professor at the University of Hong Kong’s department of microbiology, said the chance of getting infected was low if the person did not have wounds on their skin.
“But if one has a wound or a broken skin condition such as eczema, and gets into contact with the saliva that contains the virus, they can get infected,” Ho told a radio programme on Thursday.

Flu-like symptoms such as fever and chills, muscle aches, fatigue and headache can develop from three days to a month after infection. The infected person may then develop small blisters in the wound or body area that came into contact with the monkey, followed by other symptoms such as shortness of breath and nausea.
The virus may spread to other parts of the body and cause inflammation of the brain and spinal cord, leading to muscle coordination problems, brain damage or even death.
3. Is the infection treatable?
Despite a relatively high mortality rate, antiviral drugs are available as preventive care and treatment for those exposed to or infected with the B virus. Experts debate at which point antiviral treatment should be discontinued, although some argue that lifelong suppressive antiviral therapy may be needed.
4. What should I do if I am exposed to B virus?
Ho said people injured by monkeys should rinse the wound with water and soap within five minutes – the time the virus needed to enter a person’s cells as shown by past studies.
He said the wound should be washed for 15 minutes to wash away the virus before it entered the cells. The person should then seek medical attention immediately.
Hongkongers defy warnings, feed monkeys as man fights for life with B virus
5. How do you prevent B virus infection?
There is no vaccine for a B virus infection. People should stay away from macaque monkeys and refrain from touching or feeding them.
The Agriculture, Fisheries and Conservation Department has urged people not to eat in front of monkeys and avoid direct eye contact with them to avoid being perceived as provocative. People should also avoid carrying plastic bags and hide any in a backpack.
Illegal feeding of wild animals including monkeys is subject to a maximum fine of HK$10,000 upon conviction under the Wild Animals Protection Ordinance.
Laboratory workers should wear personal protective equipment, such as lab coats, gloves and a face shield, when working with macaques.

6. Where are Hong Kong’s monkeys and are attacks common?
Authorities estimate Hong Kong has about 1,800 wild monkeys distributed in 30 social troops. They are mainly found in Kam Shan, Lion Rock and Shing Mun country parks.
Since 2009, the Ocean Park Conservation Foundation has operated a programme to neuter monkeys to control their population in the long run.
In a reply to lawmakers in 2017, the government said it had not received reports of monkeys attacking people from 2014 to 2016.
Over the same period, around 440 to 550 monkey nuisance cases, such as searching for food in residential areas, were reported annually.
The department said on Thursday that the city recorded between 212 and 307 monkey nuisance cases annually from 2021 to 2023, and 76 such reports were made in the first three months this year. Those cases included monkeys searching for food in residential areas.


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Hong Kong has reported its first human case of B virus, but how do you catch it and how deadly is it?

Wild monkeys are generally found in three of Hong Kong’s country parks. Photo: Dickson Lee

Residents have been urged to stay away from Hong Kong’s wild monkeys. Photo: Dickson Lee

Dr Ho Pak-leung says the chance of people without skin wounds getting infected is low. Photo: RTHK

Hong Kong’s first human case of B virus fighting for his life after monkey attack

Wild monkeys in Hong Kong. Authorities have urged residents to keep their distance from the animals. Photo: Felix Wong

The man is currently in a critical condition in Yan Chai Hospital. Photo: K. Y. Cheng

Top scientists from Hong Kong, worldwide to join forces under new alliance backed by Aids-cure pioneer to fight future pandemics

A world-renowned virologist has called for scientists around the globe to come together to stay ahead of emerging infectious diseases. Photo: Shutterstock

Columbia University’s Professor David Ho is acclaimed for discovering the efficacy of a cocktail antiretroviral treatment for Aids. Photo: Sammy Heung

Professor Ho is teaming up with HKU microbiologist Professor Yuen Kwok-yung as part of a global alliance to combat future pandemics. Photo: Foon Lee

News

Hong Kong

Health & Environment

First Hong Kong patient with B virus, a 37-year-old man, in a critical condition in hospital
Since the virus was discovered in 1932, about 50 human infections have been recorded, with 21 deaths


First Hong Kong patient with B virus, a 37-year-old man, in a critical condition in hospital.


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Provide background, definition and detail of a specific topic, helping the reader understand how something works or what has happened in the past.  (Eg. What is Nafta? US and Mexico are on the verge of revising trade deal.)


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Explainer | Hong Kong has reported its first human case of B virus, but how do you catch it and how deadly is it?

First Hong Kong patient with B virus, a 37-year-old man, in a critical condition in hospital Since the virus was discovered in 1932, about 50 human infections have been recorded, with 21 deaths

1. What is B virus and is it fatal?

First Hong Kong patient with B virus, a 37-year-old man, in a critical condition in hospital

Since the virus was discovered in 1932, about 50 human infections have been recorded, with 21 deaths