In September 2017, a patient in Hong Kong was diagnosed with rat hepatitis E virus after inflammation of the liver was observed.
Investigators from the University of Hong Kong’s Department of Microbiology have identified the first case of rat hepatitis E virus in a human.
A 56-year-old man underwent a liver transplant at a hospital in Hong Kong in May 2017 after suffering from chronic hepatitis B, according to the investigators. In September 2017, hospital physicians observed inflammation of the liver, but the absence of symptoms associated with a transplant rejection.
Physicians ruled out any infection from the transplant and donors and the patient was subsequently tested for liver infections hepatitis A and hepatitis E, both of which were negative.
After performing genetic sequencing of a specimen from the patient, investigators noticed similarities with the rat strain of hepatitis E; therefore, they gave the man antiviral treatment for his infection. The man has since been cured.
As such, a new test is needed to detect this virus in humans, according to the investigators.
“The rat hepatitis E virus isolated from the patient’s specimen is very distantly related to the human hepatitis E virus,” Dr. Siddharth Sridhar, clinical assistant professor at the University of Hong Kong, said at a press conference. “So, usual laboratory testing for hepatitis E virus including the [polymerase chain reaction] PCR test that would normally be used to detect the hepatitis E virus will completely miss this infection.”
The manner in which the virus is transmitted is not known at this time. Further epidemiological evidence is needed to determine the root of transmission.
However, the investigators revealed that the ill patient had been living in an apartment adjacent to a room where residents brought their trash to be disposed of; this trash room has been confirmed to contain rats. The investigators hypothesize that potential methods of transmission, in this case, could include the consumption of food contaminated with rat droppings, exposure to environmental conditions contaminated with rat droppings, or the occurrence of a rat bite.
Health officials in the area located near the patient’s apartment had previously tested rats found in the ill man’s neighborhood—one rat was found to have the hepatitis E virus.
In response to this isolated case, the investigators are advocating for stricter rodent control in urban areas. However, Dr. Sridhar stressed the fact that this case occurred in an immunocompromised patient so the threat of rat hepatitis E virus in humans with normal immunity needs to be further explored.
Unanswered questions regarding the risks and threat to individuals with normal immunity will be determined in the future once more cases of rat hepatitis E virus in humans are identified. By identifying other cases, investigators hope to determine how big this threat is and if a serious outbreak of rat hepatitis E virus could occur in the future.
"Rat hepatitis E virus now joins this list of infections as an important pathogen that may be transmitted from rats to humans," Dr. Sridhar said at the press conference.
Rat hepatitis E virus was discovered in Germany in 2010 and has been previously documented in rats in various regions of the world, including the United States.