Rare Disease Month: Nipah Virus—It Is From Bats!

Rare Disease Day and Month

(Adobe Stock 1237822754 by Elena)

February is Rare Disease Month, a time to raise awareness of uncommon but serious illnesses. In this article, Rebecca Leach, MPH, BSN, RN, CIC, an Infection Control Today^®’s editorial advisory board member, explores the Nipah virus—a rare, highly virulent zoonotic disease with significant public health concerns. Understanding its transmission, impact, and prevention strategies is crucial in combating emerging infectious threats.

Zoonotic diseases are diseases that spread from animals to humans. Emerging infectious diseases and novel viruses often result from zoonotic spillover. Rare infectious diseases are classified as such because they have a low prevalence in the general population. Nipah virus is an infectious disease that falls into both categories.

Nipah virus is a zoonotic disease that has high mortality and morbidity for humans. First identified in 1999, the virus was discovered in Malaysia and Singapore, where an outbreak occurred in swine that spread to humans who had close contact with the sick animals.¹ The natural reservoirs of the Nipah virus are fruit bats and flying foxes.¹ There is no disease associated with Nipah virus in the fruit bats, which makes an ideal host for the virus. The natural habitats of the fruit bats include Malaysia, Bangladesh, India, Cambodia, and Indonesia.²
Nipah virus is a single strand RNA based virus of the Paramyxoviridae family.² The virus is highly virulent and, like other RNA viruses, has the potential for a high level of mutations.

Transmission occurs with direct contact with infected animals, ingesting raw food contaminated by infected animals, or contact with bodily fluids of an infected person. The incubation period is typically 4 to 14 days. Signs and symptoms of an infected person include fever, headache, cough, sore throat, and difficulty breathing. The illness typically lasts 3 to 14 days; however, if severe disease develops, a person can have encephalitis, coma, and possible death. Based on studied outbreaks, the mortality rate for humans infected with Nipah virus range from 30% to 70%.³

Since the early symptoms are nonspecific, early identification of cases can be challenging without accompanying epidemiological evidence. Lab tests are available to detect the Nipah virus, including polymerase chain reaction (PCR) and live culture assay.⁴ No treatments are available for Nipah virus infection; supportive care is the current recommendation.

Once a positive case is identified, strict infection control practices must be implemented to prevent spread to close contacts and health care providers. Isolation precautions, including contact and droplet precautions, are recommended, with airborne precautions as an option depending on transmission circumstances.

The best way to prevent future outbreaks is to limit exposure to the reservoir, fruit bats. Humans are at increased risk of acquiring the infection due to the virus spillover from the bats to domestic stock. Human impact on the environment also increases the possibility of exposure. Deforestation and over-farming encroach on the natural habitats of the fruit bats, bringing potential host animals into contact with infected reservoirs.

One of the most recent outbreaks of Nipah virus was also one of the largest, with over 30 individuals infected. This was related to infections of domestic pigs and then resulted in human-to-human spread.³ Other outbreaks have resulted from eating date palm sap or fruits that infected fruit bats had contaminated.

As with other rare infectious diseases, there is limited attention to not only developing treatment or vaccination options but also limited diagnostics and early detection. Animal health surveillance would give an early clue of potential outbreaks in farm animals or livestock. Having rapid testing available in the areas of high occurrence is also necessary, but due to limited public health resources, it proves a challenge. Vaccination research has started for the Nipah virus; however, there have not been any promising human trials yet.

As with any zoonotic disease, the changes in reservoir habitats combined with viral mutations could expand the host bats to other areas of the globe and increase human-to-human spread. If either occurs, or both simultaneously, then the risk of a large-scale outbreak is high. In the meantime, local populations at risk for encountering infected bats or livestock need to have the knowledge and resources available to prevent transmission, such as keeping bats away from the fruit and date palm juice, having appropriate protective equipment when handling sick animals, and resources for appropriate hand hygiene when caring for ill patients.

References

1. CDC. About Nipah virus. Updated February 23, 2024. Accessed February 24, 2025. https://www.cdc.gov/nipah-virus/about/index.html
2. The Lancet. Nipah virus: A reemerging public health concern. Z Cui, J Li, L Meng, Z Zhang. Volume 5(3), E212. Published online December 20, 2023. Accessed February 24, 2025. https://www.thelancet.com/journals/lanmic/article/PIIS2666-5247(23)00361-0/fulltext
3. P Devnath, HMAA Musad. Nipah virus: a potential pandemic agent in the context of severe acute respiratory syndrome coronavirus 2 pandemic. New Microbes New Infections. Volume 41. March 19, 2021.
4. World Health Organization. Nipah Virus. Published May 30, 2018. Accessed February 25, 2025. https://www.who.int/news-room/fact-sheets/detail/nipah-virus