Nipah virus as a biological weapon

Nipah virus is an RNA virus belonging to the henipavirus group and is classified as a Category C agent by the U.S. Centers for Disease Control and Prevention, indicating its potential use as a biological weapon. First identified in 1998 during an outbreak among pigs in Malaysia, Nipah virus has since caused significant mortality in both animals and humans, particularly in regions of South Asia. The virus is primarily transmitted from fruit bats to animals and humans, with symptoms ranging from respiratory distress to severe neurological complications, often resulting in a mortality rate exceeding 50%.

While there is currently no specific treatment for Nipah virus infection, supportive care is essential, and research into vaccines shows promise. Notably, outbreaks can occur beyond the natural habitats of fruit bats, potentially arising from exposure to infected animals or meat, underscoring the need for vigilance in animal husbandry and food safety. The possibility of human-to-human transmission and the risk of bioterrorism prompt ongoing research and public health preparedness efforts to mitigate the impact of this emerging pathogen.

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DEFINITION: RNA virus of the henipavirus group in the family Paramyxoviridae that causes disease characterized by fever and severe influenza-like symptoms with high mortality in animals and humans.

SIGNIFICANCE: Nipah virus is an emerging pathogen with an increasing incidence of deaths in humans and domestic animals. The US Centers for Disease Control and Prevention classified the Nipah virus as a Category C agent, a category that includes emerging pathogens that have the potential to be engineered to cause mass dissemination but are not considered major bioterrorism threats, in the mid-2000s.

The Nipah virus was first discovered during outbreaks in 1998–99 when domestic pigs in Malaysia experienced an outbreak of disease initiated by fruit-eating bats. Subsequent outbreaks occurred in India and Bangladesh. Outbreaks of the closely related Hendra virus, another henipavirus also spread by fruit bats, have occurred in horses in Australia. All these outbreaks were characterized by transmission from animals to humans, with high mortality. Regions of the world where fruit bats (also called flying foxes) are found include much of South and Southeast Asia, Madagascar, and Australia. These regions can be anticipated as sites of natural outbreaks of Nipah virus and Hendra virus, especially wherever domestic animals are raised in proximity to fruit bats.

Nipah virus is identified by its epidemiology, pathology with high mortality, and laboratory tests on the blood and tissue of victims. It can be detected by serological tests that identify antibodies to viral proteins in the blood. The virus has also been isolated from patients and grown in cells in culture, then further identified by antibody reactions to surface proteins of the virus and through its ultrastructure as seen in the electron microscope. Nipah virus RNA (ribonucleic acid) is detectable by the reverse transcriptase-polymerase chain reaction (RT-PCR) method. Forensic labs should retain blood and tissue samples from suspected victims of the virus for future tests and should take care to preserve the chain of evidence.

In animals, the symptoms of Nipah virus are mainly respiratory; in humans, symptoms are both respiratory and neurological. In humans, symptoms begin with fever and headaches, progressing to nausea, vomiting, weakness, coughing, and ultimately to respiratory distress and possibly very high fever and encephalitis. No effective treatment has yet been developed beyond supportive care. The mortality rate for humans who contract the Nipah virus is estimated at 40 to 75 percent depending on the level of clinical management and varying from one outbreak to another. Vaccines have been developed that show promise; tests with hamsters, cats, and horses indicate that they offer significant protection from the disease. By 2026, several vaccine candidates were under research and development, but none had completed the regulatory process for worldwide approval.

Transmission of the Nipah virus from fruit bats to animals most likely takes place through exposure to bat saliva, urine, or feces. Transmission to humans is most likely through exposure to saliva and other bodily fluids, with documented human-to-human transmission occurring primarily through close personal contact rather than widespread airborne spread.

Outbreaks of Nipah virus infection outside the regions of fruit bat territory may be expected to have different causes, such as exposure to infected meat or to animals shipped from affected regions. One outbreak in humans took place because workers in a Singapore slaughterhouse were exposed to infected pigs from neighboring Malaysia in 1999. In the twenty-first century, a number of outbreaks occurred in India, and in early 2023, an outbreak in Bangladesh resulted in eleven infections and eight deaths. In 2025, additional outbreaks were reported in Bangladesh, resulting in four confirmed fatal cases and underscoring the continued seasonal reemergence of the virus in the region. Recurrent outbreaks have also been documented in India’s state of Kerala, particularly in the Kozhikode district, highlighting the persistence of Nipah virus transmission in specific ecological and geographic settings. In early 2026, confirmed Nipah virus infections were reported in eastern India, including cases among healthcare workers in West Bengal, prompting containment measures and renewed public health surveillance. Potential exists for other episodes to take place outside the regions where Nipah virus occurs naturally, such as through transmission from travelers exposed during stays in fruit bat territory, through accidents in clinical or research laboratories, or through bioterrorist attacks. The World Health Organization assesses the public health risk posed by Nipah virus as moderate at the national level in affected countries and low at the global level, reflecting the virus’s limited transmissibility despite its high case-fatality rate.

In addition to the risk to public health, institutes such as the National Institute of Allergy and Infectious Diseases (NAID) and CDC have categorized Nipah virus as a potential biological weapon owing to its properties and the lack of strong preventive measures to contain outbreaks.


Bibliography

Anderson, Burt, et al., editors. Microorganisms and Bioterrorism. Springer, 2006.

Flint, S. J., et al. Principles of Virology: Molecular Biology, Pathogenesis, and Control of Animal Viruses. 2nd ed., ASM Press, 2004.

Ghosh, Debosmita. “Nipah Virus in West Bengal: 5 Cases Reported, Prompting Quarantine and Precautionary Measures.” NDTV, 17 Jan. 2026, www.ndtv.com/health/nipah-virus-in-west-bengal-5-cases-reported-prompting-quarantine-and-precautionary-measures-10770870. Accessed 19 Jan. 2026.

Hsu, V. P., et al. “Nipah Virus Encephalitis Reemergence, Bangladesh.” Emerging Infectious Diseases, vol. 10, 2004, pp. 2082–87.

Mohapatra, Priyanka, et al. “Addressing the Nipah Virus Threat: A Call for Global Vigilance and Coordinated Action.” Clinical Infection in Practice, vol. 24, 2024, doi:10.1016/j.clinpr.2024.100390. Accessed 19 Jan. 2026.

Mustaq, Adnan, et al. "Category C Potential Bioterrorism Agents and Emerging Pathogens." Infectious Disease Clinics of North America, vol. 20, no. 2, 2006, pp. 423-441.

National Institutes of Health. “NIH Launches Clinical Trial of mRNA Nipah Virus Vaccine.” National Institute of Allergy and Infectious Diseases, 2025, www.niaid.nih.gov/news-events/nih-launches-clinical-trial-mrna-nipah-virus-vaccine. Accessed 19 Jan. 2026.

Sun, Yan-Qun, et al. “Mapping the Distribution of Nipah Virus Infections: A Geospatial Modelling Analysis.” The Lancet Global Health, vol. 8, no. 7, July 2024, pubmed.ncbi.nlm.nih.gov/38969474/. Accessed 22 Jan. 2026.

United States, Centers for Disease Control and Prevention. Nipah Virus. CDC, www.cdc.gov/nipah-virus/about/index.html. Accessed 19 Jan. 2026.

University of Oxford. “Oxford Vaccine Against Deadly Nipah Virus Granted European Medicines Agency PRIME Designation.” University of Oxford, 9 June 2025, www.ox.ac.uk/news/2025-06-09-oxford-vaccine-against-deadly-nipah-virus-granted-european-medicines-agency-prime. Accessed 19 Jan. 2026.

World Health Organization. Nipah Virus. WHO, www.who.int/news-room/fact-sheets/detail/nipah-virus. Accessed 19 Jan. 2026.

World Health Organization. Nipah Virus Infection – Bangladesh. 17 Feb. 2023, www.who.int/emergencies/disease-outbreak-news/item/2023-DON442. Accessed 19 Jan. 2026.

World Health Organization. Nipah Virus Infection – India (Kerala). 6 Aug. 2025, www.who.int/emergencies/disease-outbreak-news/item/2025-DON577. Accessed 19 Jan. 2026.