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Nipah Virus

Emerging infectious disease


Updated September 19, 2004

In January and February 2004, 47 people in Bangladesh became infected with Nipah virus in two outbreaks; 35 of them died (74% mortality rate). Infectious disease specialists were already familiar with the deadly Nipah virus. In 1998-1999 in Nipah, Malaysia, and soon after in Singapore, people began developing brain inflammation (encephalitis), and in many cases this quickly progressed to coma and death. In all, 265 people were infected and 105 of them died (40% mortality rate).

A new virus emerges
The cause of the outbreak in Malaysia was found to be a previously unknown virus, named Nipah after the area where it was identified. Nipah virus is part of the family of viruses called Paramyxoviridae, but researchers have found enough unique characteristics of Nipah and another virus, Hendra, to give them their own genus, Henipavirus. Because 90% of the infected people in the 1998-1999 outbreak were pig farmers or had contact with pigs, pigs were tested for the virus and found to be infected. The disease was highly contagious among pigs, spread by coughing. Eventually 1.1 million pigs were destroyed on the Malay peninsula to try to contain the outbreak.

Animal transmission not certain
How the Nipah virus infected the pigs is not entirely clear. Researchers have found antibodies to Nipah virus in 5 species of bats in the area. It is believed that the bats are natural hosts for the virus, meaning that they carry the virus but are not affected by it. Scientists speculate that bat wastes or fruit contaminated by bat saliva fell into pig pens and were consumed by pigs, who then became infected.

2004 outbreak worries researchers
Although person-to-person transmission of Nipah virus has not been reported, the outbreaks in Bangladesh are cause for concern. No contact with pigs or any other infected domestic animals was found among the victims. Therefore, it can’t be ruled out that infected people passed Nipah virus to other people. This would be cause for alarm, since worldwide travel would give the virus the ability to reach many more people outside of the geographic area of an outbreak.

Adding to the mortality rate for Nipah virus infection is that there is no known cure for it. Some infected individuals who received the antiviral drug ribavirin early in their illness had less severe symptoms. Treatment is mostly focused on managing fever and the neurological symptoms. Severely ill individuals will be hospitalized and may require the use of a respirator (ventilator).

Preventing future outbreaks of new viruses
Scientists did not know of the existence of Nipah virus until people started to become ill and die. Researchers who study infectious diseases worry that there are more lethal viruses in animals that might be transmitted to humans. Encroaching on the habitat of animals by deforestation or by building homes in wildlife areas brings people into contact with animals in new ways. This may permit animal viruses to cross over into humans. Scientists hope to understand this process of transmission better to prevent future outbreaks of new deadly viruses.

Information for this article was taken from:
- CBSNEWS.com. The virus hunters. April 28, 2004.
- Centers for Disease Control and Prevention. Hendra virus disease & Nipah virus encephalitis.
- Choi, C. Nipah’s return. Scientific American, September 2004.
- Mackenzie, J.S., et al. (2000). Emerging viral diseases of Southeast Asia and the Western Pacific. Emerging Infectious Diseases, vol. 7, no. 3.
- World Health Organization. (2001). Nipah virus.

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