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
- Malaysia 1998-1999- First documented appearance of the virus
- Singapore- 1999
- Siliguri, West Bengal, India- 2001
- Bangladesh- 2001-2013
- Nadia, West Bengal, India- 2007
- 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
- Direct contact with:
- infected bats,
- infected pigs,
- Other NiV infected people
- Transmission through respiratory droplets, saliva, contact with infected tissues, other bodily secretions
- Consumption of fruit or fruit products contaminated with urine or saliva of infected bats- Indirect transmission
- The secondary wave of transmission occurs from human-human contact and is most challenging for health authorities to combat
- 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
- In the Malaysia outbreak, transmission occurred primarily through contact with infected pigs.
- No occurrence of person-to-person transmission was reported in this outbreak.
- 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
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:
- A multi-disciplinary team from the National Centre for Disease Control was sent to Kerala to investigate and respond to the disease outbreak.
- Infection prevention and control measures have been strengthened in health care
- Acute fever and acute encephalitis syndrome (AES) surveillance upgraded across hospitals in Kerala
- Hospital and community surveillance strengthened
- 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
- Isolation of patients; quarantines have been set up
- Kerala government has issued travel advisories
- Other state governments have also issued advisories on prevention. Example: Delhi
- 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 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:
- 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
- Inadequate and often dysfunctional public health infrastructure; shortage of health workforce
- 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
- 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.
- Research is needed to better understand the ecology of bats and Nipah virus.
- 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.
- The key to controlling any disease outbreak and reducing mortalities is early detection of the outbreak in communities and livestock
- Effective disease surveillance system, functioning across the country including in rural areas, is the need of the hour for disease preparedness and mitigation
- International collaboration on disease surveillance needs to be further strengthened
- Enforcing standard infection control practices to avoid human-to-human infections
- Awareness of transmission and symptoms among all stakeholders