Over the past two years, a handful of people in Hong Kong have contracted the strain of hepatitis E virus (HEV) that typically infects rats, CNN reports.

Experts who have analyzed these cases remain mystified as to the specific means by which the virus has been transmitted from rats to people.

Hepatitis E infects the liver and can lead to jaundice, fever and an enlarged liver.

The first report of human acquisition of rat HEV occurred in Hong Kong in 2018 and was written up as a case study in Emerging Infectious Diseases. To date, 10 more cases of rat hep E have been diagnosed in humans. On April 30, a 61-year-old man with abnormal liver function became the most recent person diagnosed.

Experts believe these cases may represent only the tip of the iceberg and that hep E may be passing from rats to humans in any number of other places around the world.

The strain of HEV specific to humans is typically transmitted through drinking water contaminated with feces.

As to how the rat version of the virus was transmitted to humans, researchers theorize that rat feces might have contaminated the drinking water or something else ingested by those who have contracted the virus.

However, the man in question in this most recent case of transmission does not have rats or rat feces in his home. What’s more, no one he lives with has developed symptoms of infection, nor has he recently traveled.

To read the CNN article, click here.

To read the Emerging Infectious Diseases article, click here.