DH follows up on Nipah virus infection cluster in India
In light of reports indicating a cluster of a Nipah virus infection in a certain region of India, the Centre for Health Protection (CHP) of the Department of Health (DH) said today (January 26) that it has proactively sought further information from the World Health Organization (WHO) and Indian health authorities. The CHP is also conducting health screenings on inbound travellers from the affected area who exhibit suspected symptoms, with an aim of promptly referring suspected cases to hospitals for investigation. Currently, there are no imported or local cases of Nipah virus infection in Hong Kong.
Preliminary information indicated that a hospital in Kolkata, West Bengal, India, has recorded five confirmed cases of Nipah virus infection since mid-January of this year. The cluster was mainly due to nosocomial transmission and primarily involved healthcare workers, with no reported deaths or cross-border transmissions to date. Approximately 100 close contacts have been quarantined and tested in India. The CHP's current risk assessment indicates a low risk of importation of Nipah virus into Hong Kong.
Nipah virus was first identified during outbreaks in Malaysia and Singapore from 1998 to 1999, affecting pig farm workers and individuals with close contact with pigs. It can affect various animals, including pigs, horses, goats, sheep, cats and dogs. Over the past two decades, multiple outbreaks of human Nipah virus infections were recorded in Bangladesh and India, typically occurring between December and April. Transmission primarily occurs through the consumption of raw date palm sap contaminated by fruit bats. India's most recent outbreak occurred in Kerala in mid-2025, involving four cases.
"Nipah virus infection is an emerging zoonotic disease. Fruit bats are the natural host for the virus. The virus is mainly transmitted through direct contact with sick animals via their contaminated respiratory droplets, nasal secretions and tissues. It can also be transmitted via consuming food contaminated with urine, droppings or saliva from infected bats, usually fruits or fruit products (particularly raw date palm sap). Human-to-human transmission is also possible through close contact with contaminated secretions and excretions of infected persons. Such transmission has been reported in patients' household and healthcare settings," the Controller of the CHP, Dr Edwin Tsui, said.
Patients infected with Nipah virus can be asymptomatic. Early symptoms include flu-like symptoms, such as fever, headache, vomiting, sore throat and muscle aches. Other symptoms include dizziness, drowsiness and a decrease in consciousness. Severe cases may develop complications such as pneumonia, seizure, encephalitis, coma or even death. The case fatality rate ranges from approximately 40 per cent to 75 per cent. Among the patients who survive acute encephalitis, around 20 per cent of them may have persistent nerve problems. Currently, there is no specific treatment or medication for Nipah virus infection. The mainstay of treatment is limited to supportive care. Symptoms usually start to develop around four to 14 days after exposure, but onset may occur as late as 45 days.
"Hong Kong has the ability to detect infections of unknown causes and emerging infectious diseases at boundary control points and in hospitals. On the immigration level, the DH conducts medical assessments for sick travellers at all boundary control points and refers them to hospitals for medical examinations as needed. The CHP has a robust communicable disease surveillance and notification mechanism that enables medical professionals to report suspected cases. So far, no cases of Nipah virus infection have been recorded. Although there are no direct flights between Kolkata and Hong Kong, the CHP will step up health screenings for passengers arriving from India at the airport as a precautionary measure. Port Health staff have been arranged to carry out temperature screenings for travellers at relevant flight gates, perform medical assessments on symptomatic travellers and refer suspected cases with potential public health implications to hospitals for examination," said Dr Tsui.
Dr Tsui reminded the public to take the following measures to reduce infection risk if travel to Nipah virus-affected areas is unavoidable:
- Avoid contact with wild animals or sick farm animals, especially bats, farmed pigs, horses, domestic and feral cats.
- Avoid areas where bats are known to roost.
- Observe good personal hygiene; wash hands frequently with liquid soap and water, especially after contact with animals or their droppings/secretions, and after taking caring of or visiting sick people.
- Observe food hygiene by thoroughly washing and peeling fruits before consumption. Fruits with signs of bat bites or found on the ground should not be consumed. Avoid drinking raw date palm sap, toddy or other juice.
The CHP will monitor the situation and implement appropriate prevention and control measures based on risk assessments to safeguard public health and the well-being of citizens.
