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.