Two months ago, Hong Kong health authorities revealed that a local resident had been infected with a strain of hepatitis that was previously only found in rats.
Though the 56-year-old man has since been treated and cleared by doctors of the rat hepatitis E infection, the city revealed this week (Nov. 19) that there was a second case of a human contracting the virus—a 70-year-old Hong Kong woman, reports the South China Morning Post.
The World Health Organization estimates that 20 million people are infected by the hepatitis E virus every year, but these are the only two known cases of rat hepatitis E being passed to humans.
The two patients lived in the same district, just 3 kilometers (1.9 miles) apart, but don’t appear to be connected, according to Siddharth Sridhar, a clinical assistant professor at the University of Hong Kong involved in both cases. Sridhar added that the second case proved the rat variant of the hepatitis E virus could be transmitted to people.
“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,” Sridhar told the Telegraph (paywall).
In the first case, which was diagnosed last year, the man had received a liver transplant, an operation that requires immune-suppressant drugs to prevent the body from rejecting the donor organ. Researchers suspect that he contracted the disease after eating food contaminated by rat feces. Aside from consuming contaminated food and water, hepatitis E, not just the rat variant, can also be transmitted by eating undercooked meat.
The 70-year-old woman also had a weakened immune system, according to Hong Kong’s health authorities. She was admitted to a hospital in May last year after developing symptoms including abdominal pain and malaise. Samples collected at the time showed she had been infected with the rat hepatitis E virus, which was reported to Hong Kong’s Centre for Health Protection this month. Her infection cleared within weeks without medication (paywall).
Sridhar estimates that about 1% of rats carry the hepatitis E virus, based on studies in Shenzhen and other parts of Guangdong province. “It is reasonable to assume that the situation in Hong Kong is similar,” he said.