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Nipah and Hendra viral encephalitis

Adeeba Kamarulzaman, MBBS, FRACP
Khean Jin Goh, MBBS, FRCP
Section Editor
Martin S Hirsch, MD
Deputy Editor
Jennifer Mitty, MD, MPH


Nipah and Hendra viruses are two related zoonotic pathogens that have emerged in the Asia-Pacific region. Both are RNA viruses belonging to the Paramyxoviridae family and grouped under the genus Henipavirus, since they share antigenic, serological, and ultrastructural characteristics and differ from other paramyxoviruses [1-4]. Another virus in the genus is the non-pathogenic Cedar virus [5].

Nipah virus caused an outbreak in pigs and humans in Malaysia and Singapore between 1998 and 1999, and has caused recurrent human outbreaks in Bangladesh and West Bengal, India since 2001 [6-13]. An outbreak of henipavirus infection, most likely due to Nipah or a Nipah-like virus, occurred in the Philippines in 2014 [14]. Hendra virus infections affecting horses and humans have occurred in Australia since 1994 [15-18].


Nipah virus was initially discovered when it caused an outbreak of viral encephalitis among pig farmers in Malaysia. The virus was named after a village in Malaysia, where the infected patient lived. Since then, there have been several outbreaks of acute Nipah encephalitis in various districts in Bangladesh, in the neighboring district of Siliguri in India, and in the Southern Philippines [13,14,19].

Epidemiology of Nipah virus infection — The outbreak in Malaysia was initially thought to be Japanese encephalitis (JE), which is endemic in Asia. However, certain features were not consistent with this diagnosis: the occurrence of encephalitis among adults rather than children, the clustering of cases in the same household, and a history of illness in pigs belonging to the affected farmers [7,9]. Furthermore, a high number of patients had been vaccinated against JE [7,9]. (See "Arthropod-borne encephalitides", section on 'Japanese encephalitis virus'.)

Animal reservoirs — The primary animal reservoirs of henipaviruses are bats of the genus Pteropus [20-25]. Antibodies against Nipah antigens were found in bats from Malaysia and Bangladesh, and the virus was isolated from urine of bats of the species Pteropus hypomelanus roosting in the East Coast of Malaysia [10,20,24]. Since then, serological evidence of Nipah virus infection have been found in 23 species of bats from 10 genera in regions as widely spread as Yunan and Hainan Island in China, Cambodia, Thailand, India, Madagascar, and Ghana in West Africa [25].

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Literature review current through: Nov 2017. | This topic last updated: May 02, 2016.
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