Viral Encephalitis Outbreak in Malaysia Declining

News release

The outbreak of viral encephalitis that has affected parts of the states of Perak, Negri Sembilan and Selangor in Malaysia appears to be declining. The number of hospital admissions over the past week has diminished although 41 patients remain hospitalized. Since the beginning of the outbreak in October 1998 until 19 April 1999, there have been a total of 256 cases and 98 deaths. Of the deaths for which tests have been completed, 40 were due to Nipah virus, 8 to Japanese encephalitis (JE) and 17 had a dual infection of JE and Nipah virus.

Culling of pigs has proven effective in eliminating the source of human infections. During the culling operation 883 324 pigs were slaughtered in Negri Sembilan and Selangor. Another 14 905 are scheduled for culling in the state of Perak.

Although there is still a chance of new cases appearing in other areas due to the movement of pigs, the coordinated control measures adopted by the Health and the Veterinary Services of the Malaysian Government appear to have been successful.

WHO and international experts have also worked with government and non-governmental agencies to control the disease.

A programme to survey all of the more than 1000 pig farms in Malaysia for Nipah virus will soon get underway. A system to sample the farms on a regular basis will then be put in place to prevent another such outbreak from taking place in the future.

In addition to the ongoing clinical and laboratory investigations, a number of epidemiological studies are being carried out to investigate how the virus is transmitted and if any animals in addition to pigs are involved.

More than 400 health workers have been in the affected areas interviewing and testing farmers, their families, abattoir workers, pork sellers, veterinarians, soldiers involved in the culling operation and hospital staff to determine how the virus is transmitted.

At the same time, studies of fruit bats and other possible animals, including goats and dogs, are proceeding. At one point, there was concern that horses were affected but all tests done so far have proved negative. Testing will continue.

For more information, contact Mr Charles Raby, Public Information Officer at (632) 528 9983 or email:

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