Nipah virus infection

Nipah virus (NiV) is a zoonotic paramyxovirus classified within the genus Henipavirus of the family Paramyxoviridae, designated as a Biosafety Level-4 agent ^[3][4]. It is typically transmitted to humans from infected animals or contaminated food products, but person-to-person transmission has also been documented ^[1][2]. The virus causes a spectrum of human illness ranging from asymptomatic infection to acute respiratory disease and fatal encephalitis, and it can produce severe disease in livestock such as pigs ^[1][2][5].

Human infection spans a broad clinical spectrum, from asymptomatic cases to acute respiratory illness and, at its most severe, encephalitis ^[1][2]. Most symptomatic patients develop fever together with neurological manifestations such as headache and confusion and/or pulmonary symptoms such as cough and difficulty breathing; chills, fatigue, drowsiness, dizziness, vomiting, and diarrhoea are also frequently reported ^[2]. Severe disease may progress to brain swelling, and is particularly associated with patients presenting with neurological signs, often culminating in death ^[2][5]. The incubation period typically ranges from 3 to 14 days, with rare instances of up to 45 days reported ^[2].

Nipah virus was first identified in 1998 during an outbreak among pig farmers in Malaysia, followed in 1999 by an outbreak in Singapore linked to the importation of sick pigs; neither country has reported new outbreaks since 1999 ^[1]. Outbreaks have since been detected in India and Bangladesh since 2001, with Bangladesh experiencing almost annual events and India reporting periodic outbreaks across several parts of the country ^[1]. An additional outbreak occurred in the Philippines in 2014, with no subsequent cases reported there ^[1]. Reported case-fatality rates vary widely from approximately 40% to 80% across settings and studies, reflecting differences in clinical severity and the capacity of local health systems ^[3][4][5].

Fruit bats of the Pteropodidae family, distributed across parts of Asia and Australia, are the natural reservoir of Nipah virus and do not typically develop clinical disease when infected ^[1]. Human transmission can occur through direct contact with infected animals such as bats, pigs, or horses, or through consumption of fruits and fruit products (including raw date palm juice) contaminated by infected bats ^[1][2][3]. Sustained person-to-person transmission has been documented, including in health-care settings among patients' families, caregivers, and health workers, with nosocomial risk amplified by overcrowding and poor ventilation ^[1][2][5].

Prevention rests on reducing zoonotic spillover and interrupting person-to-person spread through a One Health framework that addresses bat, livestock, and human transmission pathways ^[5]. Public-health measures supported by WHO and partners include surveillance, strengthened laboratory capacity, clinical management protocols, infection prevention and control in health-care facilities, community engagement, and avoidance of raw date palm juice or fruits potentially contaminated by bats ^[1][5]. Rapid diagnosis and strict implementation of infection control are considered essential to contain outbreaks, given the current absence of approved vaccines or specific antivirals ^[3][5].

1. 1World Health Organization. Nipah virus fact sheet [Internet]. cited 4 Sept 2026.Available from: https://www.who.int/news-room/fact-sheets/detail/nipah-virus
2. 2World Health Organization. Nipah virus infection [Internet]. cited 4 Sept 2026.Available from: https://www.who.int/health-topics/nipah-virus-infection
3. 3Madhukalya R et al. Nipah virus: pathogenesis, genome, diagnosis, and treatment. Appl Microbiol Biotechnol. 2025 Jul 1. PMID: 40593310. doi: 10.1007/s00253-025-13474-6.PubMed: https://pubmed.ncbi.nlm.nih.gov/40593310/
4. 4Angeletti S et al. Molecular epidemiology and phylogeny of Nipah virus infection: A mini review. Asian Pac J Trop Med. 2016 Jul. PMID: 27393089. doi: 10.1016/j.apjtm.2016.05.012.PubMed: https://pubmed.ncbi.nlm.nih.gov/27393089/
5. 5Aditi et al. Nipah virus infection: A review. Epidemiol Infect. 2019 Jan. PMID: 30869046. doi: 10.1017/S0950268819000086.PubMed: https://pubmed.ncbi.nlm.nih.gov/30869046/