Second human case of rat hepatitis discovered in Hong Kong

A 70-year-old woman in Hong Kong has been infected with rat hepatitis, making the city home to the world’s only two known cases of the virus jumping from rodents to humans.

Scientists found the case while testing blood samples of patients who previously contracted the hepatitis E virus after discovering an initial case of the rat version in humans a few months ago.

The cases have raised concern that humans are susceptible to contracting the disease via rats. 

“It’s not a one-off thing – it can jump to humans, and the people who seem to be susceptible are individuals with weak immunity,” said Dr Siddharth Sridhar, a microbiology professor at the University of Hong Kong, one of the scientists who discovered the two rat-to-human hepatitis cases. 

“Rats are very versatile – they’re basically all over the world, and Hong Kong is no exception.”

He said it was important for city officials to focus on controlling the rodent population, doctors to test patients for the rat hepatitis variety, and the public to be careful in eating properly prepared food.

Experts announced the first case, found in a 56-year-old man, in September. The patient had undergone a liver transplant surgery in May 2017, and subsequently developed abnormal liver symptoms. Clinical tests later showed that he had contracted the rat hepatitis virus. 

Researchers ruled out infection via his blood and organ donors. Instead, they found his housing complex had piles of rubbish and evidence of rodent infestation, including droppings.

The patient was cured over a few months with the help of antiviral drugs, though it is likely it took longer given his weakened immune system after surgery. In the most recent instance, the woman’s symptoms cleared within weeks and didn’t require medication.

Both were believed to have been infected in 2017, and lived in the same Hong Kong neighbourhoods. However, scientists haven’t found a direct link between the two cases.

Like many other cities around the world, Hong Kong officials have long battled rats, which were described to one local paper as being “as big as kittens.”

Hepatitis affects the liver and is usually transmitted through contaminated food and water – for instance, by eating under-cooked meat or coming into contact with unclean water.

The specific strain, hepatitis E, infects around 20 million people a year and is most prevalent in East and South Asia, according to the World Health Organisation.

Symptoms can vary from mild discomfort to very severe; some infections become life-threatening.

The rat version, first discovered in 2010 in Germany, has a “very significant genetic difference” from the strains typically known to infect humans up until now, Dr Sridhar said.