New Virus Fingered in Malaysian Epidemic

Scientists have identified a virus that has killed at least 95 people in Malaysia in the last 6 months, most of them pig farm workers. The culprit was officially named the Nipah virus Sunday, for the small town from whence the strain was first identified. The virus replicates in pigs and is related to the Hendra virus, which first surfaced in Australia in 1994, killing two people and over a dozen horses.

The virus first struck in late September. Victims came down with high fever and encephalitis (an inflammation of the brain), and some died. From the symptoms, health authorities assumed they were dealing with Japanese encephalitis (JE). But a vaccination campaign and massive fogging of Culex mosquitoes, which transmit JE, didn't halt the outbreak. And scientists were puzzled by some peculiarities: The disease killed pigs, which JE doesn't do; it was felling many adult humans, whereas JE kills mostly children; and it seemed to affect only those who had been in close contact with pigs, while their family members stayed healthy, which doesn't fit the pattern of a mosquito-borne disease.

The riddle was solved after medical microbiologist Lam Kai Sit of the University of Malaya and his colleague Chua Kaw Bing started hunting for other possible agents. On 5 March, the duo isolated a new virus from blood and cerebrospinal fluid samples, which, in tests at the Centers for Disease Control and Prevention (CDC) in Atlanta, reacted with antibodies to the Hendra virus. Sequencing the viral genome showed that the Nipah and Hendra viruses are about 80% similar.

The researchers suspect the virus is present in pig lungs and urine and that humans can get infected by inhaling aerosols; no cases of person-to-person transmission are known. And it's unclear how the virus got into the pigs in the first place. The Hendra virus has been found in four species of Australian fruit bats, and Australian and CDC researchers are now looking to see whether Malaysian fruit bats host the new Nipah virus.