Situation at a glance
Between 1 January and 29 August 2025, the International Health Regulations National Focal Point (IHR NFP) for Bangladesh notified WHO of four confirmed fatal Nipah virus (NiV) infection cases, temporally unrelated, reported from four different districts across three separated geographical divisions (Barisal, Dhaka, and Rajshahi) in Bangladesh.
NiV infection is a zoonotic disease transmitted to humans through infected animals (such as bats or pigs), or food contaminated with saliva, urine, and excreta of infected animals.
It can also be transmitted directly from person to person through close contact with an infected person.
Fruit bats or flying foxes (Pteropus species) are the natural hosts for the virus.
Human NiV infection is an epidemic-prone disease that can cause severe disease in humans and animals, with a high mortality rate, and outbreaks primarily occurring in South and South-East Asia.
Since the first recognized outbreak in Bangladesh in 2001, human infections have been detected almost every year.
To date, Bangladesh has documented 347 NiV cases through its Nipah surveillance system established to detect and respond to outbreaks promptly, with a case fatality rate of 71.7%
There are currently no specific drugs or vaccines for NiV infection; intensive supportive care is recommended to treat severe respiratory and neurologic complications.
Public health efforts should focus on raising awareness of risk factors, promoting preventive measures to reduce exposure to the virus, and on early case detection supported by adequate intensive supportive care.
The Ministry of Health and Family Welfare in Bangladesh has implemented several public health measures with support from WHO.
WHO assesses the overall public health risk posed by NiV at the national and regional levels to be moderate; the risk of international disease spread is considered low.
Description of the situation
Between 1 January and 29 August 2025, the Bangladesh IHR NFP notified WHO of four confirmed fatal Nipah virus (NiV) infection cases that occurred at different times from four separate districts across three different divisions (Barisal, Dhaka, and Rajshahi) of Bangladesh.
All cases were confirmed through Reverse Transcription Polymerase Chain Reaction (PCR) and Enzyme-Linked Immunosorbent Assay (ELISA) testing, and no epidemiological links were reported to have been identified between the cases.
The first case was a young adult woman from Pabna district, Rajshahi division, with symptom onset on 25 January. She was admitted to a community hospital on 26 January and referred to another hospital the next day. She died on 28 January, and laboratory confirmation of NiV was received on 29 January. A total of 96 contacts were reported to be identified, and all tested negative for NiV.
The second case was an adult man from Bhola district, Barisal division, who developed symptoms on 13 February and was admitted to hospital on 19 February. He was transferred to another hospital the next day and died on 22 February. NiV infection was confirmed on 21 February. A total of 71 contacts were reportedly identified, and all tested negative for NiV.
The third case was an adult man from Faridpur district, Dhaka division, with symptom onset on 17 February. He was admitted to hospital on 25 February and died the same day. NiV infection was confirmed on 26 February. A total of 66 contacts were identified, and all tested negative for NiV.
The fourth case was a male child from Naogaon district, Rajshahi division, with symptom onset on 3 August. He was admitted to a hospital on 8 August and moved to the intensive care unit the following day. He died on 14 August. Samples collected on 10 August tested positive for NiV on 22 August. An outbreak investigation team was deployed the same day. A total of 72 contacts were identified, and samples from 11 symptomatic contacts were collected. Six tested negative, while the results for the remaining are awaited. This case was reported outside the typical season (December to April).
The first three cases had a history of consuming raw palm sap. However, the fourth case had no history of consuming raw palm sap, and the likely source/s of infection remain under investigation. None of the cases appears to be linked to each other. Fruit bats, the known reservoir for NiV, are present in the affected regions.
Since the report of the first case in 2001, human infections have been reported almost every year, with case fatality ratios (CFR) varying between 25% (in 2009) and 100% (in 2024). In 2024, five laboratory-confirmed fatal cases of NiV were reported from Bangladesh (Figure 1, Figure 2).
Figure 1. Annual number of reported Nipah virus cases and deaths, 1 January 2001 – 9 September 2025, Bangladesh.
Source: Institute of Epidemiology, Disease Control and Research, Bangladesh. https://iedcr.portal.gov.bd/site/page/d5c87d45-b8cf-4a96-9f94-7170e017c9ce/-
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Figure 2. Distribution of Nipah cases in Bangladesh, 2001-2025, as of 14 August 2025
Epidemiology
Nipah virus infection is a zoonotic disease transmitted to humans through infected animals (such as bats or pigs), or food contaminated with saliva, urine, and excreta of infected animals. It can also be transmitted directly from person to person through close contact with an infected person. Fruit bats or flying foxes (Pteropus species) are the natural hosts for the virus.
The incubation period ranges from 4 to 14 days. However, an incubation period of up to 45 days has once been reported. Laboratory diagnosis of a patient with a clinical history of NiV infection can be made during the acute and convalescent phases of the disease by using a combination of tests. The main tests used are RT-PCR from bodily fluids and antibody detection via ELISA.
Human infections range from asymptomatic infection to acute respiratory infection (mild, severe), and fatal encephalitis (brain swelling).
Infected people initially develop symptoms including fever, headaches, myalgia (muscle pain), vomiting and sore throat. This can be followed by dizziness, drowsiness, altered consciousness, and neurological signs that indicate acute encephalitis. Some people can also experience atypical pneumonia and severe respiratory problems, including acute respiratory distress. Encephalitis and seizures occur in severe cases, progressing to coma within 24 to 48 hours.
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The CFR in outbreaks across Bangladesh, India, Malaysia, and Singapore range from 40% to 75%, depending on local capabilities for early detection and clinical management. There are currently no drugs or vaccines specific for NiV infection. Intensive supportive care is recommended to treat severe respiratory and neurologic complications. Henipavirus nipahense (Nipah virus) is considered a priority pathogen for the acceleration of medical countermeasures (MCMs) to respond to epidemics and pandemics as part of the WHO R&D Blueprint for Epidemics.[1]
Public health response
Several public health measures have been implemented by local authorities, including:
-- The Ministry of Health and Family Welfare has conducted investigations in collaboration with other sectors through a One Health coordinated approach.
-- Contact tracing has been carried out around the identified cases, with continuous follow-up.
-- Surveillance effort has been strengthened and extended beyond the regular active and passive surveillance to ensure early case detection.
-- Health education and awareness campaigns, including community engagement and advocacy, are ongoing under the supervision of civil surgeons (the head of the district health systems).
-- Nipah information leaflets have been distributed in endemic areas as part of risk communication efforts.
-- Clinicians have been sensitized and alerted to NiV.
-- Prompt sample collection, transportation, and testing were conducted at the reference laboratories.
The support provided by WHO:
-- Provided event communication support at national and international levels, including the timely submission of an official IHR notification to WHO.
-- Closely followed up on NiV infection field investigations to support robust data collection and effective contact tracing.
-- Supported case management, including infection prevention and control measures at household and health facility levels to prevent secondary cases.
-- Monitoring of the evolving outbreak situation, especially during the ongoing Nipah season, including support for data compilation, assessment of epidemiological patterns, risk factors, and geographic spread.
-- Provided technical support to the government in developing public health messaging for the prevention and control of the outbreak.
WHO risk assessment
Nipah virus (Henipavirus nipahense) is a zoonotic pathogen with a high CFR (40-75%) and no licensed vaccine or treatment. Its reservoirs are fruit bats or flying foxes (bats in the Pteropus genus), which are distributed in the coastal regions and on several islands in the Indian ocean, India, south-east Asia and Oceania. The virus can be transmitted to humans from wild and domestic animals. So far, outbreaks have only been reported in Asia; however, as the disease can be transmitted by domesticated animals and secondary human-to-human transmissions are also possible, it has considerable epidemic or pandemic potential. The disease is endemic in Bangladesh, with seasonal outbreaks linked to bat activities and cultural practices such as the consumption of raw date palm sap. Seasonal outbreaks occur between December and May, coinciding with the harvesting of date palm sap.
To date, Bangladesh has documented 347 NiV disease cases, with a case fatality rate of 71.7%. Nearly half of these cases (n=162) were primary cases with a confirmed history of consuming raw date palm sap (DPS) or tari (fermented date palm sap), while 29% resulted from direct person-to-person transmission. In 2025 to date, four fatal cases of NiV infection have been reported in Bangladesh; however, none of them appear to be linked to each other. While three of the cases presented a seasonal pattern, clustered during the first two months of 2025, the fourth case presented outside of the usual season, with no history of consuming raw date palm sap, and the possible source of infection remains unknown.
Based on the current available information, WHO assesses the overall public health risk posed by NiV at the national level to be moderate, taking into consideration the high case fatality rate, no availability of specific drugs or vaccines for NiV infection and the difficulty of early diagnosis. Although sensitive and specific laboratory methods exist, the symptoms during the first phase are not specific and could potentially delay a timely diagnosis, outbreak detection and response. In addition, fruit bats (Pteropus spp.) are the natural reservoir of NiV, and they are present in Bangladesh and repeated spillover of the virus from its reservoir to the human population has been demonstrated. Despite ongoing efforts at risk communication and community engagement to raise awareness, there is continued consumption of raw date palm sap in the community.
People infected with NiV may remain asymptomatic. Although human-to-human transmission has been reported in previous outbreaks, it has been less frequent in recent years. The yearly number of NiV infection cases reported in Bangladesh has remained under 10 since 2016, except for 2023, when 13 cases were reported. Strong public health measures are implemented in Bangladesh to detect and control outbreaks, including sentinel NiV surveillance, established since 2006, and the availability of Rapid Response Team (RRT) at both the central and district levels, along with the capacity to rapidly test samples.
For neighbouring countries – India and Myanmar - WHO assesses the public health risk posed by NiV at the regional level to be moderate. While there has not been any report of previous cross-border transmission, the risk of spread still remains, given the shared ecological corridor of fruit bats and the occurrence among domestic animals and human cases previously reported in both countries. India has demonstrated capacity and experience in controlling previous NiV outbreaks.
WHO assesses the public health risk posed by NiV at the global level to be low, as there have been no confirmed spread of cases outside Bangladesh.
WHO advice
In the absence of a licensed vaccine or specific therapeutic treatment for Nipah virus disease, the only way to reduce or prevent infection in people is by raising awareness of the risk factors. This includes providing guidance on measures that people can take to reduce exposure to the Nipah virus, and case management should focus on delivering timely supportive care, supported by an effective laboratory system. Intensive supportive care is recommended for treatment of severe respiratory and neurologic complications.
Public health educational messages should focus on:
-- Reducing the risk of bat-to-human transmission
-- Efforts to prevent transmission should first focus on decreasing bat access to date palm sap and other fresh food products. Freshly collected date palm juice should be boiled, and fruits should be thoroughly washed and peeled before consumption. Fruits with signs of bat bites should be discarded. Areas where bats are known to roost should be avoided.
-- Reducing the risk of human-to-human transmission.
-- Close unprotected physical contact with NiV-infected people should be avoided. Regular hand washing should be carried out after caring for or visiting sick people.
-- Protective measures include guidelines to limit the spread of the disease both in households and hospitals (use of protective equipment, isolation, and safe contact with medical staff).
-- The options to prevent secondary transmissions are active case finding, contact tracing, isolation and quarantine of cases and their contacts.
-- Controlling infection in health care settings
-- Health and care workers caring for patients with suspected or confirmed infection, or handling specimens from them, should implement standard precautions for infection prevention and control at all times.
-- As health care-associated infections and occupational infections of Nipah virus have been reported, in health-care settings, contact and droplet precautions should be used in addition to standard precautions, including the use of single-rooms for isolation. Airborne precautions are required in addition to contact precautions during aerosol-generating procedures.
-- Enhanced environmental controls in health-care settings are advised, including twice daily environmental cleaning and disinfection of all surfaces in the patient care area of patients with suspected or confirmed NiV infection, and to ensure inpatient care areas meet or exceed the minimum ventilation rate of at least 60 litres per second per patient.
-- Samples taken from people and animals with suspected NiV infection should be handled by trained staff working in suitably equipped laboratories.
Based on the currently available information, WHO does not recommend any travel and/or trade restrictions.
Further information
-- World Health Organization. WHO South-East Asia Regional Strategy for the prevention and control of Nipah virus infection 20232030 https://www.who.int/publications/i/item/9789290210849
-- World Health Organization. Technical brief: Enhancing readiness for a Nipah virus event in countries not reporting a Nipah virus event. Interim Document, February 2024. https://www.who.int/publications/i/item/9789290211273
-- Nipah virus [Fact sheet]. Geneva: WHO; 2018. Available from: https://www.who.int/news-room/fact-sheets/detail/nipah-virus
-- World Health Organization. Nipah virus infection. https://www.who.int/health-topics/nipah-virus-infection#tab=tab_1
-- Nipah Situation Dashboard, Institute of Epidemiology, Disease Control and Research (IEDCR). https://www.iedcr.gov.bd/site/page/d5c87d45-b8cf-4a96-9f94-7170e017c9ce/-
-- Nipah Virus Transmission in Bangladesh https://www.iedcr.gov.bd/site/page/03d6e960-2539-4966-8788-4a12753e410d/-
-- Foodborne Transmission of Nipah Virus, Bangladesh https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3291367
-- Nipah Virus Disease: Epidemiological, Clinical, Diagnostic and Legislative Aspects of This Unpredictable Emerging Zoonosis https://www.mdpi.com/2076-2615/13/1/159
-- Tackling a global epidemic threat: Nipah surveillance in Bangladesh, 2006–2021 https://pmc.ncbi.nlm.nih.gov/articles/PMC10529576/
-- The Ecology of Nipah Virus in Bangladesh: A Nexus of Land-Use Change and Opportunistic Feeding Behaviour in Bats https://pmc.ncbi.nlm.nih.gov/articles/PMC7910977/
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[1] CEPI and WHO urge broader research strategy for countries to prepare for the next pandemic: https://www.who.int/news/item/01-08-2024-cepi-and-who-urge-broader-research-strategy-for-countries-to-prepare-for-the-next-pandemic
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Citable reference: World Health Organization (18 September 2025). Disease Outbreak News: Nipah virus infection in Bangladesh. Available at: https://www.who.int/emergencies/disease-outbreak-news/item/2025-DON582
Source: World Health Organization, https://www.who.int/emergencies/disease-outbreak-news/item/2025-DON582
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