Open Outbreak

Nipah virus infection

Also known as: Nipah, NiV, henipavirus, Henipavirus nipahense

Nipah virus infection is a rare but serious disease caused by Nipah virus, a virus that normally circulates in fruit bats. People can be infected after contact with infected animals, by eating or drinking food contaminated by bats, or through close contact with an infected person. Illness ranges from no symptoms to severe disease affecting the brain or lungs. WHO says the incubation period is usually 3 to 14 days, but rare cases up to 45 days have been reported. Across outbreaks in Bangladesh, India, Malaysia and Singapore, WHO reports a case fatality ratio of 40% to 75%, with differences between outbreaks partly reflecting how quickly cases are found and how much supportive care is available. There is no licensed vaccine and no specific approved antiviral treatment. Care is mainly supportive, such as oxygen, ventilation, fluids, nutrition, and treatment of complications. Outbreaks have been reported in parts of Asia, especially Bangladesh and India, and WHO continues to monitor sporadic cases and small clusters.

Key facts

TransmissionFrom infected fruit bats and other animals to humans; through contaminated food such as raw date palm sap or fruit products; and through close contact with infected people, including in households and health-care settings.
IncubationUsually 3 to 14 days; rare reports up to 45 days.
Case fatality40% to 75% across reported outbreaks in Bangladesh, India, Malaysia and Singapore, depending in part on detection and clinical management.
Reproduction numberunknown
VaccineNo licensed human vaccine; candidate vaccines are in development, including a subunit vaccine that entered Phase I testing.
TreatmentNo specific approved treatment. Early intensive supportive care is recommended; investigational antibody approaches have been discussed in the literature, but they are not licensed standard treatment.
ReservoirFruit bats or flying foxes of the Pteropodidae family, especially Pteropus species.
Endemic regionsOutbreaks have been reported in Bangladesh, India, Malaysia, the Philippines and Singapore; fruit-bat hosts are widespread across South and Southeast Asia and parts of Oceania.

Transmission

Nipah virus is mainly an animal-to-human infection, but it can also spread between people. WHO says the natural hosts are fruit bats, and people can be infected by direct contact with infected bats or other animals such as pigs or horses. Infection can also follow eating or drinking contaminated food, especially raw date palm sap or fruit products contaminated with bat saliva, urine, or droppings. In Bangladesh and India, person-to-person spread has been documented, especially among family caregivers and in health-care settings after close contact with a sick patient. WHO notes that spread is more likely in crowded, poorly ventilated hospitals when infection prevention measures are weak. The usual incubation period is 3 to 14 days, though rare longer incubations up to 45 days have been reported. A single, widely accepted basic reproduction number is not given in the WHO material retrieved here, so it is best described as unknown.

Symptoms and severity

Nipah virus infection does not always look the same. Some people have no symptoms, while others develop fever and symptoms affecting the brain or lungs. WHO lists headache, confusion, cough, difficulty breathing, chills, fatigue, drowsiness, dizziness, vomiting and diarrhoea among common features. Severe disease can progress to encephalitis, meaning inflammation and swelling of the brain. WHO says seizures and coma can follow quickly in severe cases. Respiratory disease can also be severe, including pneumonia or acute respiratory distress. The disease is serious: WHO reports that the case fatality ratio across outbreaks in Bangladesh, India, Malaysia and Singapore has ranged from 40% to 75%. That figure varies by outbreak and is influenced by how fast cases are recognized and how much intensive supportive care is available. WHO also notes that about 1 in 5 survivors may have long-term neurologic problems.

Treatment and vaccines

There is no licensed vaccine and no specific approved drug treatment for Nipah virus infection in the WHO sources retrieved here. Treatment is therefore mainly supportive. WHO says early diagnosis helps clinicians start supportive care sooner, and that high-quality supportive medical care can prevent deaths. This can include oxygen, ventilation, dialysis if needed, careful fluids and nutrition, and treatment of complications such as brain swelling or pneumonia. WHO’s 2026 disease-outbreak report also states that intensive supportive care is recommended for severe respiratory and neurologic complications. Several vaccines are under development, but they are still candidates rather than licensed products. A 2021 NPJ Vaccines paper reported that a human subunit vaccine formulation based on the Hendra virus attachment glycoprotein had entered a Phase I clinical trial. Literature also discusses monoclonal antibodies and other experimental approaches, but these remain investigational and should not be described as established care.

Where it occurs

Nipah virus infection has been reported in a limited set of countries, but the animal hosts are more widespread. WHO says human cases were first reported in Malaysia in 1998, followed by Singapore in 1999, with no new outbreaks reported from those two countries since then. Since 2001, outbreaks have been detected in Bangladesh and India. WHO says Bangladesh has reported outbreaks almost every year since, while India has had periodic outbreaks, including recent events in Kerala and West Bengal. WHO also notes an outbreak in the Philippines in 2014 with no new cases since then. The natural reservoirs are fruit bats of the Pteropodidae family, especially Pteropus species, which are distributed in parts of Asia and Oceania. That broad bat distribution matters because it means spillover risk is linked not just to country borders but to local contact between bats, domestic animals, food collection practices, and people.

Recent history

This site’s archive lists 10 WHO-notice events for Nipah since 1996. The pattern is not one of steady global spread, but of recurring small outbreaks and sporadic cases, especially in South Asia. WHO items retrieved here include Bangladesh in 2023, 2024, 2025 and 2026, and India in 2023, 2025 and 2026. In Bangladesh, WHO described the 2023 outbreak as unusual compared with the previous seven years, with 11 cases and eight deaths reported by mid-February. In India, WHO reported six confirmed cases in Kerala in September 2023, four confirmed cases in Kerala in 2025, two health-care worker cases in West Bengal in January 2026, and one confirmed case in Kerala in June 2026 with no secondary cases identified by 2026-06-18. WHO’s fact sheet says Bangladesh has outbreaks almost every year, while India reports them periodically in several parts of the country.

What to watch

The main warning signs would be changes that suggest Nipah is becoming easier to spread or harder to control. One is spread into new regions or repeated outbreaks outside the usual pattern in Bangladesh and India. Another is clearer, sustained person-to-person transmission, especially beyond households and hospitals, because that would increase the chance of larger outbreaks. WHO’s recent India reports are somewhat reassuring on this point only in the narrow sense that extensive contact tracing in June 2026 found no secondary cases by 2026-06-18, but WHO also says additional cases could not be excluded because the infection source was not identified. Other important signals are failures in infection prevention in crowded health facilities, animal or food exposures that become more common, and any evidence that investigational vaccines or treatments remain unavailable if a larger outbreak occurs. Continued absence of a licensed vaccine or specific treatment keeps preparedness dependent on surveillance, isolation, contact tracing, and supportive care.

Updated