Recent Nipah virus notifications in India

Two cases of Nipah virus infection have been reported in India. According to the report, two nurses tested positive for the disease in the Indian state of West Bengal. It is unclear whether the nurses were exposed to the disease during travel to a village in the Nadia district of West Bengal (close to the Bangladesh border) or while treating a patient with a severe respiratory tract infection. 

These are the first cases in almost 20 years for West Bengal. 

Why is this important?

A cluster of infections in health service providers is always a concern as it raises the question of an index case responsible for transmitting the disease. 

More than 190 people are now under home quarantine but no further cases have been reported.

What is Nipah virus?

Nipah is a serious viral disease which is transmitted from animals to humans. There is also human to human transmission (in a clinical or close family setting) and from food.

It is thought to infect a wide range of animals. It has a range of clinical conditions including muscle aches and pains, respiratory tract infections and encephalitis. The case fatality rate is estimated to be between 40 and 75%.

Origin, hosts and global spread

Pteropus fruit bats are the natural host of the virus. They do not show disease. Fruit is infected through their bodily fluids (secretions or urine). 

It was first recognised in Malaysia in 1998 in a disease outbreak amongst pigs. Other animals were infected during this outbreak. More than 250 cases were notified and 105 deaths. It has been reported most years in Bangladesh since early 2001.  It has also been reported in Singapore, Philippines and India. 

Six laboratory confirmed cases were reported between September 12 to 15, 2023 in Kerala, Two died. 

More than 700 cases of Nipah virus disease have been reported globally since the late 90’s.

Is there any risk for overseas travellers?

The risk to travellers is very low.

Avoidance of sick animals (bats, horses and pigs) is very important in areas of risk. Travellers are also advised against consuming fallen fruit and raw date palm sap or juice. 

There is no vaccine available. 

It is interesting to note that Taiwan’s Centre for Disease Control is intending to list Nipah virus infection as a category 5 notifiable disease. Their 4-tier travel advisory system currently asks travellers to exercise caution. This means attention to the risk of exposure but no restriction to travel.

This outbreak again raises the question of fevers in returned travellers and why it is so important to quickly identify region of travel and whether exposure to serious diseases like Nipah virus is a possibility.  

Health questionnaires and screening for fever is currently in place in several airports across southeast Asia.