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High Mortality, Low Probability: The Lesser Known Dangers of Nipah Virus

First emerged in 1998 in Malaysia, the Nipah virus was found to be transmissible from animals to humans with an estimated case fatality rate of 40 to 75 percent.1 Despite not having any more cases within Malaysia and Singapore it is still present in various parts of Bangladesh and India. With high fatality rate and currently no treatment or vaccine available, there is a pressing need to boost research and development in the area.

Nipah virus, a paramyxovirus which are one group of RNA viruses closely related to Hendra viruses. Both viruses originated from bats and can spread to humans and other animals. The Nipah virus was first discovered during an outbreak in Kampung Sungai Nipah. Malaysia in 1998, hence the name Nipah virus. It then spread across the border to Singapore in March 1999. The virus outbreak was caused through the contact with pigs which resulted in respiratory and neurological disease in pigs as well as encephalitis in humans. This especially affected the farmers who were in charge of the pig farms at the time. The Malaysia-Singapore outbreak saw a total of 276 cases and 106 deaths amounting to 38 percent case fatality. In Bangladesh and India, the outbreaks were mainly caused by consumption of contaminated date palm sap and human-to-human transmission. In both countries from 2001 to 2012 there were 280 cases and 211 deaths with a staggering 75 percent case fatality. From March to May 2014 the Philippines had 17 cases with an 82 percent case fatality. Its high mortality rate is most alarming, during a recent outbreak in the Kerala State, India, in 2018, there were a total of 19 cases and 17 deaths.

The Pteropus fruit bat was found to be the main reservoir for Nipah virus, as a zoonotic disease it can spread from animals to humans and also contaminated food. Due to its ability to transmit from person-to-person, Nipah virus has been identified to have pandemic potential. It also has been alerted that geographical locations with the Pteropus fruit bat has a possibility of a viral spill over in the future. At present, the Nipah virus still remains endemic to South and Southeast Asian regions, however its high case fatality and human-to-human transmission capabilities places it in the priority list.


The Disease2

Infection by the Nipah virus in humans can result in acute respiratory infections ranging from mild to severe, and fatal encephalitis. Some infections may not present any symptoms and these humans become carriers of the virus that can cause human-to-human transmission.

Initial symptoms are typically those akin to the common flu, these include fever, headaches, myalgia, vomiting and sore throat. As the disease worsens the symptoms could progress on and the individual would experience dizziness, drowsiness, altered consciousness, and neurological signs that indicate acute encephalitis. Atypical pneumonia and severe respiratory issues may also arise, including acute respiratory distress. It was reported that the incubation period ranges from four to 14 days but could reach as long as 45 days.

Case fatality rate of the disease caused by Nipah virus is estimate to be 40 to 75 percent. However, this figure is reliant on the epidemiological and clinical capabilities of the individual country to control and contain the spread of the virus.

Those who survive usually make a fully recovery but other neurological conditions have been reported. Residual neurological consequences such as seizures and personality changes have shown to affect about 20 percent of all patients with a small number who recover shown to relapse or develop delayed onset encephalitis.

Absence of a specific treatment for Nipah virus infection has resulted in measures to only treat symptoms such as ventilation for respiratory conditions and anticonvulsants for seizures. Coupled with the high mortality rate Nipah virus has been identified by the World Health Organization as a priority for accelerated research and development.


Current Efforts for Research and Development

With no treatment and vaccine available against the Nipah virus, there is an urgent need for research and development in the area. Its high fatality rate adds on to the necessity for the formulation of therapeutics and vaccines against Nipah virus infection.

Released in May 2018, the World Health Organisation (WHO) laid out the Nipah Research and development Roadmap,3 in an effort to supply guidelines and layout strategic goals and priorities to boost the development of diagnostics, therapeutics and vaccines against the Nipah virus. Prior to that the WHO also published a document in June 2017 stating the target product profile for Nipah virus vaccine.4 This document was to provide vaccine scientists, product developers, manufacturers and funding agencies understand the considerations and product profile of the Nipah virus vaccine as laid out by the WHO.

The inaugural Nipah Virus International Conference held in 2019 – co-hosted by Duke-NUS Medical School and the Coalition for Epidemic Preparedness Innovations (CEPI)—brought together world experts in Nipah virus. In a bid to strengthen the International efforts and foster a collaborative environment to improve the capabilities in combatting this deadly virus, key strategies of each representative country were discussed.

Co-chairman of the conference’s organising committee and Director of the Emerging Infectious Diseases Programme at Duke-NUS, Professor Wang Linfa shared, “There are currently no specific drugs or vaccines against Nipah virus infection, even though the WHO has identified Nipah as a priority disease under the WHO Research and Development Blueprint.” He then also hoped that through the conference dialogue could be stimulated among experts and key stakeholders to accelerate the efforts to fight against Nipah virus infection.

Some challenges highlighted during the conference was the lack of sufficient cases for research as well as the availability of specialised laboratory equipment to contain and study the Biological Safety Level 4 virus.

Emergence of the novel coronavirus (SARS-CoV-2) in 2019 that causes COVID-19 disease has resulted in more than five million confirmed cases and more than 350,000 deaths across the world as of late May 2020. This unprecedented wide spread and infection of SARS-CoV-2 demonstrates the urgency of identifying key components of emerging diseases and engaging experts using a collaborative approach to tackle such novel viruses. [APBN]

This article was derived from the attendance at the Nipah Virus International Conference 2019.


  1. World Health Organisation, (May 30, 2018) Nipah Virus Fact sheet. Retrieved from: https://www.who.int/news-room/fact-sheets/detail/nipah-virus
  2. World Health Organisation, (May 30, 2018) Nipah Virus Fact sheet. Retrieved from: https://www.who.int/news-room/fact-sheets/detail/nipah-virus
  3. World Health Organisation, (May, 2018), Nipah Research and Development (R&D) Roadmap, Retrieved from: https://www.who.int/docs/default-source/blue-print/nipah-draft-r-d-roadmap.pdf?sfvrsn=d59dfd26_4&download=true
  4. World Health Organisation, (June, 2017) WHO Target Product Profile for Nipah virus Vaccine. Retrieved from: https://www.who.int/blueprint/priority-diseases/key-action/Nipah_virus_vaccineTPP.pdf?ua=1&ua=1
  5. Aditi, & Shariff, M. (2019). Nipah virus infection: A review. Epidemiology and infection, 147, e95. https://doi.org/10.1017/S0950268819000086
  6. Banerjee, S., Gupta, N., Kodan, P., Mittal, A., Ray, Y., Nischal, N., Soneja, M., Biswas, A., & Wig, N. (2019). Nipah virus disease: A rare and intractable disease. Intractable & rare diseases research, 8(1), 1–8. https://doi.org/10.5582/irdr.2018.01130