Nipah Virus

Nipah virus is an enveloped RNA virus that is a member of the family Paramyxoviridae, genus Henipavirus and is genetically related to Hendra virus. The name 'Nipah' comes from the Malaysian village, where the first outbreak was reported in 1998 and 1999.

Fruit bats, which are also called flying foxes (Pteropus species), are the natural animal reservoir for Nipah virus. They inhabit much of the Western Pacific, Southeast and South Asia, and Madagascar. Nipah virus infection is a bat-borne zoonotic disease transmitted to humans through contact with infected bats, livestock, or domestic animals. It can also be transmitted by ingesting contaminated palm sap or fruit. The disease can also be transmitted directly from person to person through close contact with an infected person or body fluids. 

Nipah virus was first identified as a zoonotic pathogen after an outbreak involving respiratory illness in pigs and severe encephalitis in humans occurred in Malaysia and Singapore in 1998 and 1999. During that outbreak, 265 human cases were identified in Malaysia and the case-fatality rate was 40%. Annual outbreaks have occurred in Bangladesh and parts of India since 2001. Outbreaks are seasonal and coincide with the harvesting of date palm sap which can be contaminated with infected bat droppings. More than 400 human cases have been confirmed in Bangladesh and India. Case-fatality rates have ranged from 50% to 100%. 

The incubation period usually ranges from 4 to 14 days, but an incubation period up to 45 days has been reported. Nipah virus infection in humans can range from asymptomatic infection to severe. Infected people initially develop symptoms including fever, headache, myalgia, vomiting, and sore throat. The prodrome can be followed by dizziness, drowsiness, altered consciousness, and neurological signs that indicate acute encephalitis. Some people can also develop atypical pneumonia and acute respiratory distress. Encephalitis can lead to seizures and coma within 24 to 48 hours. Most people who survive acute encephalitis make a full recovery, but long-term neurologic conditions have been reported. Approximately 20% of patients have residual neurological consequences such as seizure disorder and personality changes. 

Currently, there are no licensed vaccines or therapeutics available for the prevention or treatment of Nipah virus infection.

Nipah virus infection can be confirmed during the acute and convalescent phases of the disease by a combination of Real Time Polymerase Chain Reaction (RT-PCR) using throat and nasal swabs and serum antibody detection via enzyme-linked immunosorbent assay (ELISA). RT-PCR can also detect virus in cerebrospinal fluid, urine, and blood. 

References

World Health Organization, Nipah virus infection – Bangladesh, 17 February 2023, https://www.who.int/emergencies/disease-outbreak-news/item/2023-DON442

Centers for Disease Control and Prevention, Nipah Virus, October 19, 2022, https://www.cdc.gov/vhf/nipah/index.html

Banerjee S. et al. Nipah virus disease: A rare and intractable disease, Intractable Rare Dis Res. 2019 Feb;8(1):1-8. doi: 10.5582/irdr.2018.01130. PMID: 30881850; PMCID: PMC6409114.

CIDRAP, A Research and Development Roadmap for Nipah Virus: 2024 Update.