In 2018, a 56-year-old man, who had undergone a liver transplant, showed abnormal liver functions with no obvious cause. It was the first time that infectious disease experts at the University of Hong Kong came across such patients.
The tests on the patient showed that his immune system was responding to hepatitis E, but they could not find the human strain of the hepatitis E virus or HEV in his blood.
What is Hepatitis E?
Hepatitis E is a liver disease that can also cause jaundice, fever, and an enlarged liver. The virus comes in four different species and only one of these four was known to infect humans. The experts redesigned the diagnostic test and ran it again, and they found that the patient had rat hepatitis E, and it was the first time in history that it was found in a human.
Dr. Siddharth Sridhar, a microbiologist and one of the HKU researchers who made the discovery said that a virus that can jump from street rats to humans was detected. He said that it was such an unusual and unprecedented infection that the team wondered if it was just one rare incident and that the patient may just have been in the wrong place at the wrong time.
Unfortunately, the incident happened to numerous people. There were 10 more residents in Hong Kong who all tested positive with rat Hepatitis E, also known as rat HEV. The most recent case was that of a 61-year-old man with an abnormal liver function who tested positive on April 30. Dr. Sridhar is worried that there may be hundreds more infected undiagnosed people.
According to the World Health Organization, the human strain of hepatitis E is usually transmitted through fecal contamination of drinking water. However, the rat strain poses a new mystery, because no one knows how the patients got infected.
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Researchers have yet to identify the exact route of transmission from rats to humans, and its already been two years since the discovery. There are theories, such as patients may have drank contaminated water or handled contaminated objects, but there has been no concrete evidence.
The recent patient has experts baffled because there were no rats or rat excrement in his home, and nobody else in his household has shown symptoms. The patient also had no recent travel history. According to the statement released by the Hong Kong's Center for Health Protection or CHP on April 30, based on the available epidemiological information, the source and the route of infection could not be determined.
What experts know and don't know
Research teams and health experts have been trying to understand the new health threat since 2018. They have made some progress and their diagnostic tests have been refined and improved. They have spread awareness among the health care sector so doctors know to test for rat HEV and they also launched public awareness campaigns.
Scientists are now testing rat populations across the city to identify clusters before they can jump to humans. However, there is still so much about rat HEV that is still unknown.
Experts do not know how long the incubation period of the virus is and they are still trying to find treatment because the medication used to treat the human variant of hepatitis E ha had mixed results on patients with rat HEV. The biggest unknown that scientists are still trying to study is how the virus jumped from rats to humans.
According to Dr. Sridhar, that data that they have collected does not make much sense because people who live in rat-infested areas are not infected and the patients who are infected came from a neighborhood with low rat numbers. They are not sure whether the rats contaminate food or if there is another animal involved, and experts are still working on the missing link.
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