Nipah virus infection is a zoonotic illness that is transmitted to people from animals and can also be transmitted through contaminated food or directly between people. In people with infection, it causes a range of illnesses from asymptomatic infection to acute respiratory illness and brain swelling (encephalitis) for the most severe cases.

Cases of Nipah virus infection were first reported in 1998 and since then have been reported in Bangladesh, India, Malaysia, Philippines and Singapore. In Bangladesh and India, outbreaks have been reported periodically since 2001.

Transmission of the virus to humans can occur from direct contact with infected animals like bats, pigs or horses, and by consuming fruits or fruit products, such as raw date palm juice, contaminated by infected fruit bats. The virus can also cause severe disease in farming animals such as pigs.  

Nipah virus can also spread between people. It has been reported in health-care settings and among family and caregivers of sick people through close contact. 

For some people, Nipah virus infection may be asymptomatic. However, most people develop a fever, and symptoms involving the brain (such as headache or confusion), and/or the lungs (such as difficulty breathing or cough). Other organs can also be affected. Frequent other symptoms include chills, fatigue, drowsiness, dizziness, vomiting and diarrhoea.

 The incubation period – that is the time from infection to the onset of symptoms – ranges from 3 to 14 days. In some rare cases incubation of up to 45 days has been reported. Severe disease can occur in any patient but is particularly associated with people presenting with neurological symptoms, with progression to brain swelling (encephalitis) and, frequently, death. Careful supportive care and monitoring during this period is critical.

Most people who survive make a full recovery, but long-term neurologic conditions have been reported in approximately 1 in 5 people who recovered from the disease.

The case fatality rate of Nipah virus infection is estimated at 40–75% but can vary by outbreak depending on surveillance and clinical management in affected areas.

There are currently no approved drugs or vaccines for Nipah virus infection. WHO has identified Nipah as a priority disease for the WHO Research and Development Blueprint. A rane of candidate products are under different stages of development. 

Early intensive supportive care is recommended to treat severe respiratory and neurologic complications and can improve survival.