Nipah virus (NiV) is a zoonotic virus that spreads between animals and people. Fruit bats, also called flying foxes, are the animal reservoir for NiV in nature. NiV can also spread through pigs and other animals like goats, horses, dogs, or cats. Infection with NiV is associated with encephalitis (swelling of the brain) and can cause mild to severe illness and even death. The virus can cause a range of illnesses from asymptomatic (subclinical) infection to acute respiratory illness and fatal encephalitis. 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.

Outbreaks of Nipah virus occur almost annually in parts of Asia, primarily Bangladesh and India. The first known outbreak of NiV happened in Malaysia and Singapore in 1999, resulting in nearly 300 human cases and more than 100 deaths. During an outbreak, standard infection control practices can help prevent person-to-person spread in hospital settings.

Nipah virus infection can be prevented by avoiding exposure to sick pigs and bats in areas where the virus is present, and not drinking raw date palm sap which can be contaminated by an infected bat. Preventing Nipah virus involves infection control measures like protective equipment and disinfecting surfaces, as well as avoiding sick animals or areas with known Nipah virus outbreaks. There is currently no medication or vaccine to treat Nipah virus infection. Managing symptoms is the only way to treat Nipah virus.