Man contracts deadly B virus a month after macaque monkey encounter in Hong Kong park

By Claire Wolters | Fact-checked by Davi Sherman
Published April 15, 2024

Key Takeaways

  • A man in Hong Kong contracted B virus after being wounded by macaque monkeys. The virus is often deadly, and the man is in critical condition.

  • Hong Kong health officials are warning the public not to touch or feed macaque monkeys.

  • If wounded by a monkey, it is crucial to administer immediate first aid wound treatment and seek medical attention.

A 37-year-old man is in critical condition after being wounded by macaque monkeys at Kam Shan Country Park in Hong Kong. The man visited the park in late February and was admitted to the hospital in late March with a decreased consciousness level and fever, according to the Centre for Health Protection (CHP) of the Department of Health in Hong Kong. By April 3, he was receiving treatment in the intensive care unit. A cerebrospinal fluid specimen taken from the patient reportedly tested positive for B virus.[][]

B virus is also known as herpes simiae virus and is common in macaque monkeys but rare in humans. Humans can occasionally contract B virus from monkeys; when this happens, the presentation of the disease is often severe and deadly. In infected monkeys, B virus usually produces mild or asymptomatic disease, but in infected humans, an estimated 70% of untreated cases are fatal, according to the Centers for Disease Control and Infection (CDC). Humans who contract B virus from monkeys typically experience symptom onset within a month after exposure, which is consistent with the case in Hong Kong.[]

B virus symptoms and transmission in humans

In humans, the B virus may first manifest as flu-like symptoms. Over time, however, the infection can spread to various parts of the body. The B virus can progress to the brain and spinal cord, posing risks of brain and nerve damage and even death. 

Human infections are uncommon from any source, and contracting B virus from other humans is extremely rare. Over the years, the CDC has reported a single case of human-to-human transmission. In this case, a woman contracted B virus after coming into direct contact with her infected spouse’s lesions, according to the CDC.[]

B virus treatment in humans

People who are wounded by macaque monkeys should perform or undergo immediate first aid care, according to the CDC. This includes “thoroughly washing and scrubbing the [wounded] area with soap, concentrated detergent solution, povidone iodine, or chlorhexidine and water,” then flushing the area with running water for 15–20 minutes. If a monkey’s urine splashes into the eyes, the person should perform “repeated eye flushes for several minutes,” the CDC says.[]

Antiviral therapy, namely valacyclovir or its alternative, acyclovir, is also recommended. For people who are diagnosed with B virus, doctors should initiate intravenous treatments of acyclovir or ganciclovir, depending on whether central nervous system (CNS) symptoms are present, the CDC says. Quick treatment is imperative, as the risk of death increases when the infection spreads to the central nervous system. The most common cause of B virus–related death is respiratory failure associated with ascending paralysis, according to the CDC.

B virus diagnosis

According to the CDC, diagnostic testing for B virus is only performed at one lab in the United States: the National B Virus Resource Center at Georgia State University.

For the center to properly diagnose someone with B virus, it will need to test a specimen from the patient’s wound site. Before collecting and sending specimens to the center for testing, it is imperative to clean the wound thoroughly, as “[o]btaining specimens from wound sites before proper cleansing could force virus more deeply into exposed tissue,” the CDC says.[]

What’s happening in Hong Kong?

Following the April 3 report of the man’s condition, Hong Kong’s CHP released a notice saying it was investigating the case. A CHP spokesperson said that this was the first human B virus infection case recorded by the agency but that human B viruses cases have been recorded elsewhere, including in the United States, Canada, Japan, and “the Mainland.”

The CHP urged the public to take personal safety measures to avoid contracting B virus from monkeys, including “stay[ing] away from wild monkeys and avoid[ing] touching or feeding them.” Should someone be wounded by a monkey, the health agency advised, they should “wash the wound with running water and seek medical attention immediately.”

Keeping one’s distance and refraining from touching monkeys is the main source of protection from the virus, as there are no available B virus vaccines.

Animal-to-human infection risks

Despite their relative rarity, animal-to-human infections are possible and occurring. Other zoonotic disease transmissions have been reported in the US in recent months, including a diagnosis of human plague in Oregon in February and a death caused by Alaskapox virus (AKPV) in Alaska in January.

Related: Deadly zoonotic diseases are popping up in the US. Should doctors be on the alert?

James Giordano, PhD, MPhil, a medical researcher and Professor in the Departments of Neurology and Biochemistry at Georgetown University, says these co-occurring reports are especially concerning, as—in addition to other concerns—they may imply that these viruses are growing more intelligent and becoming increasingly capable of jumping species. Exactly how different viruses spread can vary from disease to disease, and is based on the specific mutations they may have acquired, he adds.

To investigate virus spread from an animal to a human, Dr. Giordano says that doctors and researchers must look into the nature of that spread, asking themselves what modes of contact were required for the transmission to occur.

“Does that require some direct physical contact? In other words, not just environmental contact with the cat or the animals in your house, but you actually have to touch it,” Dr. Giordano says. “[Or] does it require some kind of exchange of fluid where the cat licks, bites, sneezes on you, etc? So again, we're not only looking at the bug, we're looking at mechanism mode and vectors of transmission, and they can vary just depending on what the bug is.”

To recap, the CDC states that transmission of the B virus from macaque monkeys typically occurs when an infected macaque bites, scratches, or passes fluid or tissue to a human. The agency warns against touching the monkeys in any way.

What this means for you

Talk to your patients about public health safety while traveling, including discouraging them from touching and feeding wild animals, like macaque monkeys. These monkeys can carry the B virus, which, though rare, can be transmitted to humans and pose risks of death.

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