Nipah Virus: All you need to know


The recent spread and transmission of Nipah virus in the southern state of Kerala

What is Nipah virus?

  • Nipah Virus is a zoonotic virus- transmitted from animals to humans. Other examples include swine flu, bird flu
  • Nipah virus is highly infectious
  • The Nipah virus is a member of the genus Henipavirus in the family Paramyxoviridae
  • The virus is an RNA (ribonucleic acid) virus and mutates very fast
  • The disease was named after Kampung Sungai Nipah (Nipah River Village), Malaysia, where the first viral isolate was obtained
  • Closely related to Hendra virus
  • There is debate over whether the disease is air borne


  1. Malaysia 1998-1999- First documented appearance of the virus
  2. Singapore- 1999
  3. Siliguri, West Bengal, India- 2001
  4. Bangladesh- 2001-2013
  5. Nadia, West Bengal, India- 2007
  6. Kozikhode and Mallapuram, Kerala, India-2018- 19 people have died as of 1st June 2018


  • Fruit bats (Pteropus), popularly known as flying foxes are natural reservoir hosts of Nipah Virus


  1. Direct contact with:
  • infected bats,
  • infected pigs,
  • Other NiV infected people
  • Transmission through respiratory droplets, saliva, contact with infected tissues, other bodily secretions
  1. Consumption of fruit or fruit products contaminated with urine or saliva of infected bats- Indirect transmission
  2. The secondary wave of transmission occurs from human-human contact and is most challenging for health authorities to combat
  3. Nipah virus infection generally has a stuttering chain of transmission- Once the virus moves from bats to humans; it generally spreads to people in close contact with the patients

Difference in transmission between Malaysia and Bangladesh-India

  1. Malaysia:
  • In the Malaysia outbreak, transmission occurred primarily through contact with infected pigs.
  • No occurrence of person-to-person transmission was reported in this outbreak.
  1. Bangladesh and India:
  • The infection occurred directly from fruit bats without involvement of intermediate host (pigs).
  • Exposure has been linked to consumption of raw date palm sap and contact with bats.
  • Person-to-person transmission has been common. Most commonly seen in the family and caregivers of Nipah virus-infected patients.
  • Similar pattern observed in current outbreak

Signs and Symptoms in Humans:

  • Infection associated with inflammation of brain
  • Initial symptoms include fever, headache, respiratory problem followed by drowsiness, disorientation and mental confusion
  • These could progress to coma and ultimately to death
  • Mortality rate: High; 40-75%
  • Long term effects in those who survive: persistent convulsions, personality changes
  • Latent infections with subsequent reactivation of Nipah virus and death have also been reported


  • Viral isolation from throat and nasal swabs, cerebrospinal fluid, urine, and blood using Real Time Polymerase Chain Reaction (RT-PCR)


  • No vaccine or antiviral drug available for either people or animals.
  • Intensive supportive care with treatment of symptoms is the main approach to managing the infection in people

Preventive Measures

Guidelines from National Centre for Disease Control

Status of the Nipah Virus

  • Nipah is considered an “emerging” virus because it was discovered relatively recently- 1998-1999
  • The virus figures in the WHO’s list of epidemic threats in need of urgent research and development.
  • Centre for Disease control and Prevention (CDC) lists it as a critical potential biological weapon. This is because of its availability, ease of production and dissemination and high rates of morbidity and mortality

Government Response on Current Outbreak:

  1. A multi-disciplinary team from the National Centre for Disease Control was sent to Kerala to investigate and respond to the disease outbreak.
  2. Infection prevention and control measures have been strengthened in health care
  3. Acute fever and acute encephalitis syndrome (AES) surveillance upgraded across hospitals in Kerala
  4. Hospital and community surveillance strengthened
  5. To confirm cases of Nipah Virus Manipal Centre for Virus Research (MCVR) and the National Institute of Virology have been conducting laboratory testing
  • Since Nipah virus is considered to be a probable bioterrorism agent, in August 2017, MCVR was trained by US’s CDC to test for Nipah Virus
  1. Isolation of patients; quarantines have been set up
  2. Kerala government has issued travel advisories
  3. Other state governments have also issued advisories on prevention. Example: Delhi
  4. Disease awareness among all stakeholders. The Ministry of Health and Family Welfare (MoHFW) shared guidelines drafted by the National Centre for Disease Control with all stakeholders.

WHO Response:

  • WHO has been in contact with the Indian authorities and has been monitoring the event
  • WHO has shared various materials on preventive measures, risk communication materials on Nipah Virus
  • Indian authorities may approach WHO for support for coordinating multi-dimensional investigations

Risk Assessment by WHO:

  • WHO has assessed the risk to be low at regional and national levels
  • Based on the present situation and low level of risk, WHO did not recommend application of any travel or trade restrictions on India

Challenges before India:

  1. India has a poor record of outbreak investigations- timely detection and early warning of outbreaks is a major challenge to health authorities For example- In Muzzaffarpur, Bihar and Gorapkpur, Uttar Pradesh witnessed thousands of deaths in repeated annual outbreaks before causes were established
  2. Inadequate and often dysfunctional public health infrastructure; shortage of health workforce
  3. Large population dispersed across vast geographical area. The high density of population in most parts of the country makes disease control and prevention difficult and poses larger public health risk
  4. Lack of virology institutes

Lessons learnt from Kerala:

  • Kerala has successfully handled Nipah virus outbreak and holds important lessons for India
  • Prompt diagnosis- the detection of the virus on the very second day of outbreak is commendable
  • Further, the government’s quick response in tackling the virus is appreciated.
  • The infection control measures, measures to strengthen hospital and community surveillance have been successful in controlling the spread of disease.

Way Ahead:

  1. Research is needed to better understand the ecology of bats and Nipah virus.
  2. Research for development of intervention strategies- prevention and therapy (vaccines, anti-viral drugs). Research into development of vaccines has been ongoing in Australia and France.
  3. The key to controlling any disease outbreak and reducing mortalities is early detection of the outbreak in communities and livestock
  4. Effective disease surveillance system, functioning across the country including in rural areas, is the need of the hour for disease preparedness and mitigation
  5. International collaboration on disease surveillance needs to be further strengthened
  6. Enforcing standard infection control practices to avoid human-to-human infections
  7. Awareness of transmission and symptoms among all stakeholders
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