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.