Nipah virus

Nipah virus is a notifiable disease

Under Queensland legislation, if you suspect the presence of this disease in any animals, you must report it to Biosecurity Queensland.

Call us  13 25 23 or
Emergency Disease Watch Hotline  1800 675 888

Overview

Cause

Nipah virus is closely related to Hendra virus (first described in 1994 in Australia), and both viruses belong to the genus Henipavirus in the family Paramyxoviridae.

Description

Nipah virus can cause fatal illness in people and animals (pigs, horses, dogs, cats) and is therefore of considerable public health and veterinary concern.

Flying foxes (fruit bats of the genus Pteropus) are the natural hosts for Nipah virus, but infection in bats causes no apparent disease.

Where the disease occurs

Nipah virus was first described after a major outbreak of disease in pigs and humans in Malaysia in early 1999. The outbreak resulted in the death of 105 of 256 human cases and the culling of over 1 million pigs.

Since then there have been regular reports of clusters of cases in humans in Bangladesh and India. In contrast to the Malaysian outbreak, some of these clusters appear to involve direct bat-human transmission, and some have evident human to human transmission.

Evidence of infection with Nipah or a related virus has been found in bats from Indonesia to Africa.  

Nipah virus has not been found in Australia.

The disease in animals

This is a highly contagious disease in pigs with an incubation period of 4-14 days, during which time pigs are infectious. The majority of infections in pigs are asymptomatic, but symptomatic cases show acute fever, laboured breathing, and neurological signs such as trembling, twitching and muscle spasms. Generally, mortality is low (less than 5%), except in young piglets.

The clinical course of the disease appears to vary with age. Sows primarily present with neurological disease, but sometimes die suddenly without evident signs. In weaners and porkers, a respiratory syndrome predominates, frequently accompanied by a harsh non-productive (loud barking) cough. Apparent high mortality rates in piglets may indirectly reflect infection in sows and inability to effectively suckle piglets. 

Infection in horses, dogs and cats was also a feature of the Malaysian outbreak. Clinical signs ranged from asymptomatic to severe febrile illness, with respiratory or neurologic presentation.

As Nipah virus outbreaks in pigs have been associated with human cases, early detection of the disease is important in reducing the risk to people.

Spread of the disease

Flying foxes are the natural host for the virus. The first reported outbreak of Nipah virus infection in Malaysia in 1999 is thought to be due to a combination of factors: land-use change resulting in habitat loss, encroachment of pig farms into remnant habitat, and the local farming practice of planting fruit trees close to pig sheds. Infection spread locally, and subsequently more widely, as a result of the movement of asymptomatic pigs for trade. The majority of human cases had a history of direct contact with sick pigs or their contaminated tissues.

In the Bangladesh and India outbreaks, the primary source of infection for people appears to be consumption of fruits or fruit products contaminated with urine or saliva from infected fruit bats. 

Direct human to human transmission has also been recorded in outbreaks in Bangladesh, but it is unclear whether transmissibility reflects cultural practices or variation in strain pathogenicity.

Control of the disease in animals

During outbreaks of disease in pigs in Malaysia, the spread of infection was readily controlled by a variety of measures, including quarantining infected premises, controlling animal movements, culling pigs, burying or incinerating infected carcasses and decontaminating.

The disease in people

Nipah virus infection in people can be asymptomatic, or can result in a spectrum of clinical manifestations, from fever, muscle pain and vomiting, through to pneumonia and encephalitis. Chronic neurological symptoms and relapsing/recurring encephalitis has been recorded. The case fatality rate in people is estimated at 40-75%.

There are currently no effective treatments for Nipah virus infection and a vaccine is not available.

Last updated 29 July 2011