Jul 16, 2025
15
mins read
Nipah virus (NiV) is a deadly zoonotic pathogen known for causing severe disease in humans and animals. Characterized by acute encephalitis and respiratory symptoms, it has caused several deadly outbreaks in South and Southeast Asia, including Kerala, India.
Recognized by the WHO as a priority pathogen due to its high fatality rate (40–75%) and potential for human-to-human transmission, Nipah virus demands global attention.
Nipah virus (NiV) belongs to the family of paramyxoviruses, closely related to the Hendra virus. Both hendra and nipah viruses are known to cause severe respiratory and neurological diseases in humans and animals. The Nipah virus was first identified following an outbreak in Malaysia, where infected pigs played a significant role in transmitting the virus to humans. Since then, Nipah virus disease has been recognized as a priority disease by global health authorities due to its high fatality rate and potential for human to human transmission.
First Identified: Malaysia, 1998–99 (spread via infected pigs)
Zoonotic Nature: Circulates in animals, especially fruit bats, and occasionally spills over to humans
Transmission: Can occur from animals, contaminated food, or person-to-person
Public Health Threat: Listed by WHO for research prioritization
Table of content
Nipah virus (NiV) is a pleomorphic, enveloped virus of the family Paramyxoviridae, genus Henipavirus. Virions are relatively large (about 120–150 nm diameter) with a single lipid envelope studded by glycoprotein spikes. Inside is a helical nucleocapsid (5 nm diameter helix) protecting a non-segmented negative-sense RNA genome (~18.2 kilobases). The genome encodes six principal structural proteins: N (nucleocapsid), P (phosphoprotein), M (matrix), F (fusion glycoprotein), G (attachment glycoprotein), and L (large polymerase). (The P gene also encodes three non-structural proteins, C/V/W, by RNA editing.)
Nucleocapsid (N): wraps the RNA genome in a helical form.
Matrix (M) protein: lies just beneath the viral envelope, linking the envelope to the nucleocapsid and facilitating viral assembly and budding.
Envelope glycoproteins: NiV has two surface glycoproteins. The G (attachment) protein binds host ephrin-B2/B3 receptors to attach to cells. The F (fusion) protein mediates membrane fusion; F is cleaved into F1 and F2 to become active. Together G and F drive viral entry into host cells.
Unique feature: NiV causes characteristic reticular cytoplasmic inclusions near the endoplasmic reticulum in infected cells, a feature distinguishing it from other paramyxoviruses
Key Facts of Nipah Virus at a Glance
Aspect | Details |
Nipah Virus Family | Paramyxoviridae (Henipavirus genus) |
Reservoir Host | Fruit bats (Pteropus) – asymptomatic carriers |
First Case (Human) | Malaysia, 1998 – pig farmers |
Affected Regions | Malaysia, Bangladesh, India (Kerala), Philippines |
Fatality Rate | 40–75% (varies by outbreak and healthcare access) |
Symptoms | Fever, sore throat → seizures, encephalitis, respiratory distress |
Diagnosis | PCR, ELISA, CT/MRI (supportive) |
Treatment | No specific cure; supportive care only |
Vaccine Status | Under development (e.g. Oxford’s ChAdOx1 NiV, monoclonal antibodies) |
Nipah virus infection transmission occurs through:
1. Animal-to-Human
Contact with infected bats, pigs, goats, horses
Farms with infected pigs are known hotspots
2. Food-Borne
Raw date palm sap contaminated by bats
Partially eaten fruits or open containers
3. Human-to-Human
Exposure to bodily fluids (saliva, blood, respiratory secretions)
Common in hospital settings with poor infection control (e.g., Siliguri, 2001)
The Nipah disease spreads to humans mainly through direct contact with infected animals or their bodily fluids. Human to human transmission is also documented, particularly among infected patients in healthcare settings where infection control practices are inadequate. Contact with bodily fluids of infected patients, including respiratory secretions, increases the risk of transmission. This highlights the importance of personal protective equipment for healthcare providers managing Nipah virus cases.
Nipah virus infection has an incubation of about 4–14 days after exposure. Early Nipah virus symptoms are non-specific: fever, headache, sore throat, cough, vomiting and fatigue are common. Within days, serious signs appear: patients may develop dizziness, drowsiness, confusion and neurological deficits (acute encephalitis) Respiratory involvement is also common (atypical pneumonia or acute respiratory distress)
In severe cases the nipah disease rapidly worsens: seizures, coma and respiratory failure can develop often within 24–48 hours These hallmark features – acute encephalitis (brain inflammation) and severe respiratory distress – distinguish NiV disease. Mortality is very high (40–75%), as seen in past outbreaks (e.g. Kerala 2018).
Diagnosis requires high suspicion. Laboratory confirmation is by molecular and serologic tests: RT‑PCR detects viral RNA in throat/nasal swabs, blood or CSF, and ELISA detects NiV antibodies. Neuroimaging (CT/MRI) may show brain lesions in encephalitis. Because symptoms are non-specific, early testing in any suspect case (especially in endemic areas) is critical to start supportive care and contain spread.
The rapid progression of nipah virus from initial symptoms to severe disease underscores the need for early diagnosis and prompt medical intervention. Diagnostic tools such as enzyme linked immunosorbent assay and molecular biology techniques detecting viral RNA are essential for confirming infection.
Year | Location | Details |
1998–99 | Malaysia & Singapore | Pig-to-human transmission; 100+ deaths |
2001–Now | Bangladesh | Annual outbreaks linked to raw date palm sap; human-to-human spread |
2001 | Siliguri, India | Nosocomial spread in hospitals |
2007 | Nadia, West Bengal | Similar transmission mode |
2018–2023 | Kerala, India | Six outbreaks; bats confirmed as source; high surveillance & containment |
Emerging Risk Zones: Cambodia, Philippines, Thailand, Madagascar, Ghana (bat reservoirs present)
Several risk factors contribute to the likelihood of Nipah virus infection. Direct contact with infected bats, sick pigs, or other infected animals significantly raises the risk. Consumption of raw date palm sap contaminated by infected bats is another major risk factor in affected regions. Healthcare providers are at heightened risk due to potential exposure to infected patients and their bodily fluids. In summary the following are the major ways in which the Nipah virus (NiV) can enter the human body:
Drinking raw date palm sap
Eating fruits contaminated by bats
Handling sick pigs or livestock
Caring for NiV patients without PPE
Living near bat habitats or pig farms
There is no vaccine or proven Nipah virus treatment therefore prevention focuses on interrupting transmission. Key measures include:
Healthcare measures:
Rapidly isolate suspected NiV patients (single rooms if possible) and use full PPE.
All healthcare workers should wear gowns, gloves, eye protection and N95 respirators (or higher) when caring for suspect cases.
Implement standard + droplet/contact infection control precautions at all times. Rigorously disinfect patient rooms and equipment; wash hands thoroughly after any contact.
Farm and Animal Safety:
Limit contact between bats and livestock. Restrict bats from pig pens and orchards (e.g. cover pig sheds and palm sap collection sites).
Monitor herd health closely; report and quarantine any sudden animal illness or deaths. In an outbreak, quarantine pig farms, cull infected animals under supervision, and disinfect facilities routinely.
These measures helped contain NiV in Malaysia’s 1999 pig-farm outbreak.
Surveillance (One Health):
Integrate human, animal and environmental monitoring. Periodically sample local bat populations in known NiV “hot spots” to detect virus presence, and set up early warning systems for encephalitis clusters in humans.
This One Health approach ensures rapid detection of new outbreaks. For example, Kerala now maintains enhanced surveillance after multiple outbreaks.
Currently, there is no specific antiviral treatment approved for Nipah virus infection. Management focuses on supportive care to alleviate symptoms and address complications such as acute respiratory distress and encephalitis. However, research efforts are underway to develop effective therapies and vaccines.
Promising advances include the development of human monoclonal antibodies and vaccines by groups such as the Oxford Vaccine Group. These interventions target the viral surface proteins to neutralize the virus and prevent infection. Early diagnosis through molecular biology techniques facilitates timely treatment and containment.
Treatment Type | Status |
Supportive Care | Mainstay: fluids, oxygen, symptom management |
Ribavirin (antiviral) | Limited benefit, not conclusively proven |
Monoclonal Antibodies | In trials (e.g., MBP134, funded by CEPI in India & Bangladesh) |
Vaccines | Oxford’s ChAdOx1 NiV vaccine in clinical testing |
Progress: WHO and CEPI are prioritizing fast-track vaccine and therapeutic development under global health programs.
India’s strategy to tackle Nipah virus outbreaks, particularly in Kerala, demonstrates a proactive and evolving public health emergency response. As the nipah virus has re-emerged multiple times in Kerala, the Union and State governments, supported by the WHO, have implemented a robust Nipah virus treatment and containment strategy in India.
Key Pillars of India’s Nipah Virus Response
1. Interdepartmental Coordination
Kerala’s Health Department formed 19 core committees during recent Nipah virus outbreaks (2023) to manage surveillance, testing, logistics, treatment, and public communication.
These were supported by central agencies such as ICMR, NIV Pune, and the Ministry of Health and Family Welfare.
2. Surveillance and Contact Tracing
Conducted active house-to-house surveillance, covering over 53,000 households in containment zones.
Health teams traced and monitored high-risk contacts to interrupt human-to-human transmission.
3. Containment and Movement Restrictions
Imposed movement curbs in 9 affected villages in Kozhikode.
Enforced mask mandates, social distancing, and sealed off containment zones to prevent spread.
4. Laboratory Testing and Diagnostics
Deployed labs to test suspected human cases and environmental samples (e.g., fruit, water).
Samples were analyzed at NIV Pune, Kerala’s own VRDL labs, and mobile BSL-3 labs to speed up results.
5. Hospital Preparedness
Emergency departments were pre-equipped with ICU beds, isolation rooms, and ventilators.
Staff received refresher training on PPE use, triage protocols, and infection control.
6. Public Awareness and Misinformation Control
Released expert videos, official press updates, and community health bulletins.
Set up call centers to support public queries and curb panic.
Actively combated fake news and misinformation to maintain trust.
7. Guideline-Based Governance
India adopted a WHO-supported Nipah Virus response protocol after the 2018 outbreak.
Kerala updated these guidelines in 2019 and 2021, making them comprehensive with diagnostic, isolation, and contact-tracing protocols.
Kerala has reported four Nipah virus outbreaks in just five years—2018, 2019, 2021, and 2023-making it the most affected state in India for this bat-borne zoonotic disease. These repeated outbreaks in Kozhikode and Ernakulam districts highlight a confluence of ecological, epidemiological, and surveillance-related factors unique to Kerala. Despite the detection of Nipah virus (NiV) antibodies in fruit bats across nine other states, human outbreaks have remained limited to Kerala and historically, West Bengal.
Why Only Nipah Virus Outbreaks in Kerala?
Endemic Circulation in Bats: Fruit bats (Pteropus medius), natural hosts of Nipah virus, are widely present in Kerala. Repeated detection of NiV antibodies in bats across Kozhikode, Wayanad, Idukki, and Ernakulam suggests endemicity.
Human–Bat Proximity: Many habitations in Kerala lie near forests or within ecological zones where bat roosting is common, increasing chances of spillover.
High Clinical Vigilance: Kerala routinely tests patients with encephalitis or acute respiratory symptoms for Nipah Virus, unlike many other states.
Early Detection Protocols: Strong health infrastructure, including Calicut Medical College’s molecular virology lab, aids rapid sample testing.
Public Awareness: Citizens are well-informed about symptoms, social distancing, and reporting, contributing to timely containment.
Updated Guidelines: Kerala revised its Nipah virus protocols post-2018 and again in 2021, improving response clarity across all departments.
Evolution of Kerala’s Nipah Virus Response (2018–2023)
2018: Caught off-guard; 17 deaths in Kozhikode. Rapid state–center coordination controlled spread.
2019: Single case in Ernakulam; immediate isolation and contact tracing prevented escalation.
2021: Death of a 12-year-old boy in Kozhikode; zero secondary cases due to strict protocol.
2023: Six confirmed cases; outbreak contained through 19 core committees, ~1,300 contact tracings, and community testing.
Q. What is the Nipah virus?
A. Nipah virus (NiV) is a deadly zoonotic pathogen known for causing severe disease in humans and animals.
Q. What is the case fatality rate of Nipah virus infection?
A. Nipah virus (NiV) is associated with a high case fatality rate, typically ranging from 40 % to 75 %, depending on outbreak circumstances, healthcare access, and supportive care quality. Early detection and intensive supportive management can improve survival, but mortality remains substantially higher than for most viral encephalitides.
Q. Which animals serve as reservoir hosts for Nipah virus?
A. The primary reservoir of Nipah virus is fruit bats of the genus Pteropus, which are asymptomatic carriers. Spillover events occur when these bats contaminate food sources (e.g., date palm sap) or directly infect intermediary hosts such as pigs. Domestic animals and other wildlife may also become infected, facilitating transmission to humans.
Q. Can Nipah virus be transmitted from person to person?
A. Yes. Human-to-human transmission occurs via direct contact with the bodily fluids (saliva, respiratory secretions, urine, or blood) of infected individuals. Nosocomial spread has been documented where infection control practices are inadequate. Close caregivers and healthcare workers are at highest risk without proper personal protective equipment.
Q. Is there any vaccine or specific treatment available for Nipah disease?
A. Currently, there is no licensed vaccine or approved antiviral therapy for Nipah virus. Management relies on supportive care: hydration, respiratory support, and seizure control. Experimental approaches—including monoclonal antibodies (e.g., m102.4) and vaccine candidates (ChAdOx1 NiV)—are in clinical trials but not yet widely available.
Q.What biosafety level (BSL) is required to study Nipah virus?
A.Due to its high lethality and lack of treatment, Nipah virus research is conducted in Biosafety Level 4 (BSL‑4) laboratories. BSL‑4 facilities provide maximum containment, including full-body, air‑supplied positive‑pressure suits and specialized ventilation to prevent any risk of laboratory‑acquired infection.
Nipah virus remains a significant threat as an emerging infectious disease with the potential for severe outbreaks. Understanding its zoonotic nature, modes of transmission, and clinical manifestations is essential for healthcare providers, public health officials, and communities in Nipah virus affected countries. Implementing preventive measures, enhancing surveillance, and advancing vaccine development are critical steps to prevent Nipah virus disease and mitigate the impact of future outbreaks. Through coordinated efforts in disease control and research, the global community can better manage this priority disease and protect vulnerable populations from its devastating effects.
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