Hepatitis is a term for liver inflammation, which can be caused by several different things including medications, or alcohol, while hepatitis A, B, C, D, and E are viral infections. Symptoms of hepatitis can include loss of appetite, fatigue, unexplained weight loss, abdominal pain, and jaundice: a yellowing of the skin or eyes.
Every year, the hepatitis E virus (HEV) causes around 20 million infections in humans worldwide. All of the variants of the virus that are known to infect humans are part of the Orthohepevirus A (HEV-A) species. Rats are infected by a different species that is highly divergent from HEV-A; it's called Orthohepevirus C (HEV-C).
In 2018, a study of liver transplant patients revealed unexplained persistent hepatitis in some of the participants, and the investigators screened them for HEV antibodies. Several patients were found to have HEV, and when no strain of HEV could be found in one patient, extensive testing showed that he had an infection of rat-derived HEV-C.
Since that study, more cases have emerged. Now the rat-derived virus has been found in almost ten residents of Hong Kong. CNN reported that on April 30, the virus was found in a 61-year-old man with abnormal liver function.
A researcher at the University of Hong Kong that was involved in the 2018 study revealing the first known case, microbiologist Dr. Siddharth Sridhar, noted that hundreds more cases may be out there.
Public health authorities are still trying to determine how these people are getting infected. In the current case, no one else in the patient's household is infected, he hasn't traveled recently, and no rats or rat droppings were found in his home. "Based on the available epidemiological information, the source and the route of infection could not be determined," Hong Kong's Centre for Health Protection (CHP) said in an April 30 statement. For now, the patient remains in the hospital.
Diagnostic tests that can detect the virus are better than they used to be, and Hong Kong scientists are investigating to see where rats tend to live and testing to find out how many are infected. There is still a lot more to learn. Researchers are not only trying to find out how people are getting rat-derived HEV, they also need to learn how long the virus incubates and how to treat it.
A case identified last year is outlined in the video.
Scientists suspect that many cases of the disease may be mild and there could be far more people infected in many more cities than we're now aware of. In more vulnerable populations like the elderly or people with weak immune systems, the disease may be more serious.
"We need ongoing vigilance in the public to control this unusual infection. I really hope that public health authorities take the first step and look at how much their populations are actually being exposed to rat hepatitis E," added Sridhar.