The most recent case came a week ago; a 61-year-old man with abnormal liver function tested positive on April 30. And there might be hundreds more infected undiagnosed people out there.
Hepatitis E Virus is a liver disease that can also cause fever, jaundice and an enlarged liver. The virus comes in four species, which circulate in different animals; at the time, only one of these four was known to infect humans.
According to Dr. Siddharth Sridhar, a microbiologist and one of the University of HongKong, HKU researchers who made the discovery in 2018, the rat HEV is a virus that can jump from street rats to humans.
In 2018, a case of rat hepatitis E was for the first time discovered in a human in Hong Kong.
A 56-year-old man was diagnosed with the disease, researchers from the University of Hong Kong said. It was not previously known the disease could be passed from rats to humans.
It was such an unusual and unprecedented infection that the team wondered if it was a “one-off incident, one patient who was in the wrong place at the wrong time.”
Since that first study, 10 more Hong Kong residents have tested positive with rat hepatitis E, also known as rat HEV. The most recent case came a week ago; a 61-year-old man with abnormal liver function tested positive on April 30. And there might be hundreds more infected undiagnosed people out there, said Sridhar.
The human strain of hepatitis E is typically transmitted through fecal contamination of drinking water, according to the World Health Organization.
But the rat strain poses a new mystery: nobody knows exactly how these people are getting infected. In the two years since the discovery, researchers have yet to identify the exact route of transmission from rats to humans. They have theories — maybe the patients drank contaminated water like the usual human strain, or handled contaminated objects — but nothing’s been definitively proven.
The 61-year-old recent patient has authorities particularly stumped; there were no rats or rat excrement in his home, nobody else in his household has shown symptoms, and he has no recent travel history.
“Based on the available epidemiological information, the source and the route of infection could not be determined,” said Hong Kong’s Centre for Health Protection (CHP) in a statement on April 30. The man is still in the hospital, and the CHP’s investigation is ongoing.