Unmasking the killer

The virus that caused havoc in Malaysia may not have been JE after all

Published: Wednesday 30 June 1999

when pig farmers and farm workers in Ipoh, Malaysia started dying last year, everybody suspected that it was due to the Japanese encephalitis ( je ) virus which is spread by the Culex mosquito. In November, the health authorities declared that je was the virus behind the spate of "mysterious" deaths in the pig-farming community around Ipoh.

The announcement was followed by massive fogging of pig-farming areas, and vaccination for people living or working in "high-risk" areas (within a 2-km radius of a pig farm). But it soon became apparent that there were peculiarities about this outbreak. je has been around in Malaysia for at least 45 years and records reveal that it primarily affects the very young and the old, rarely adults. In the case of Ipoh, over 80 per cent of those who fell sick were adults.

It is now known that the Nipah virus had been at work in the majority of more than a hundred deaths so far, including those from Negri Sembilan this year. Scientists from the us Centres for Disease Control and Prevention ( cdc ) who conducted retrospective testing on survivors and tissue or blood samples from those who died in Perak found that the outbreak is predominantly caused by a new Hendra-like virus of the Paramyxoviridae family.

According to a paper titled Japanese Encephalitis Outbreak: The Kinta Experience, written by Marina Abdul Hamid, the Kinta district health officer and five others, 24 viral encephalitis cases were recorded in Ipoh between last September and mid-February. Only nine cases were confirmed as je but the rest were included as je on epidemiological grounds. But sources close to the Cabinet task force for je reveal that at least nine from this batch of Ipoh cases were actually je -negative.

The question is: Why did the doctors maintain the stand that it was je when such a large percentage of victims were negative? Henry Too, a swine expert from Universiti Putra Malaysia's Faculty of Veterinary Medicine, offers an insight. "For a disease that causes neurological disorders affecting people who are associated with pigs, je was a logical presumptive diagnosis" during the early days of the outbreak, based on the fact that it was the only documented disease that affects the brain of those who work with pigs.

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