How did a Hong Kong man become infected with rat hepatitis E?
Hong Kong health authorities are investigating the city’s first confirmed human case of rat hepatitis E virus (rat HEV) this year, renewing concerns about rodent-borne infections and urban hygiene. The case involves a 42-year-old man with chronic liver disease who tested positive for rat hepatitis E after abnormal liver function results were detected during a medical appointment.
According to Hong Kong’s Centre for Health Protection (CHP), the patient was referred to Queen Mary Hospital on May 5 after routine follow-up tests at a private hospital revealed liver abnormalities. Laboratory testing later confirmed infection with rat hepatitis E virus. Officials said the man remained in stable condition and was discharged from hospital on May 15. His three household contacts are asymptomatic but are being monitored under medical surveillance.
What Is Rat Hepatitis E?
Rat hepatitis E () is a rare strain of the hepatitis E virus carried mainly by rodents. Unlike the common human hepatitis E virus, this variant was historically believed to infect only rats and other small mammals. However, Hong Kong became the first place in the world to document human infection with rat HEV in 2018.
The World Health Organization estimates that hepatitis E causes around 20 million infections globally every year, although rat hepatitis E infections in humans remain extremely rare. Scientists still do not fully understand how the rat strain crosses into humans.
Investigators Suspect Local Transmission
Health officials believe the patient likely acquired the infection locally in Hong Kong. The man reportedly lives and works in the Hung Hom district and said he had no direct contact with rodents or visible rat infestations at his home or workplace.
Despite this, investigators warned that indirect exposure may have occurred through contaminated food, surfaces, water, or environments exposed to rat urine or droppings. Joint inspections by the CHP and the Food and Environmental Hygiene Department found minor signs of rodent activity in refuse collection rooms near both the patient’s residence and workplace. Authorities have ordered property management companies to improve sanitation and strengthen pest control measures.
Why Experts Are Concerned
Medical experts say rat hepatitis E may pose greater risks for people with underlying liver disease, weakened immune systems, organ transplants, or chronic medical conditions. According to Hong Kong health authorities, patients with chronic liver disease are more likely to develop hepatitis symptoms and abnormal liver function after infection.
Symptoms of hepatitis E can include:
- Fever
- Fatigue
- Loss of appetite
- Nausea and vomiting
- Abdominal pain
- Enlarged liver
- Jaundice in some cases
In severe situations, hepatitis E can progress to acute liver failure and death, particularly among vulnerable individuals.
Human Rat Hepatitis E Cases Remain Rare but Mysterious
Hong Kong has recorded only a small number of human rat hepatitis E cases since the first infection was identified in 2018. Authorities said the city typically reports between zero and two cases annually.
One of the biggest scientific questions remains how humans contract the virus. Earlier researchers from the University of Hong Kong suggested contaminated food exposed to infected rat droppings may be one possible route, although direct proof remains limited.
Public health experts say dense urban environments, aging infrastructure, food waste accumulation, and rodent infestations may increase the risk of exposure. Hong Kong has repeatedly faced criticism over rat infestations in crowded residential and commercial areas.
Authorities Urge Hygiene and Rodent Control
The Centre for Health Protection urged residents to practice strict food, personal, and environmental hygiene measures. Officials recommended:
- Washing hands thoroughly before eating
- Properly storing food
- Avoiding leaving food exposed at room temperature
- Cleaning surfaces using diluted bleach
- Avoiding direct contact with rodents or rodent-contaminated areas
Authorities also stressed the importance of broader rodent prevention efforts across residential buildings, workplaces, and food-handling environments.
Scientists Continue Monitoring Emerging Zoonotic Diseases
The case has again highlighted concerns about zoonotic diseases — infections that jump from animals to humans. Researchers say urban rodents can carry multiple pathogens capable of infecting people, including bacteria and viruses linked to gastrointestinal, respiratory, and liver diseases.
Although rat hepatitis E remains uncommon, infectious disease experts say continued surveillance is important because emerging animal-to-human infections can sometimes reveal previously unknown transmission pathways. Public health researchers also note that global urbanization and climate-related environmental changes may increase opportunities for zoonotic spillover events in the future.
References:
- Rat hepatitis E virus: The new kid on the block? – (https://www.journal-of-hepatology.eu/article/S0168-8278(25)00218-1/fulltext)
Source-Medindia