Beware the bats

Science News,  June 9, 2007  by B. Vastag

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Fruit bats in Bangladesh regularly trigger small outbreaks of Nipah virus, a pathogen that often causes measles-like symptoms and sometimes leads to brain inflammation and death, say researchers.

For 6 straight years, Andrew Dobson of Princeton University has recorded Nipah outbreaks in villages in Bangladesh. This year, his team has seen three emergences of the virus, with 5 to 10 cases per outbreak.

The bats feast on fruits that children later collect--even if the fruit is half-eaten-and sell to vendors who blend them into drinks. "Then, you have a nice Nipah-flavored beverage," says Dobson. Because the country's largely Muslim population shuns alcohol, purchasers drink the beverage before it can ferment, which would kill the virus.

Researchers first identified Nipah in Malaysia in 1999, when it spread from bats to pigs to people. About a third of the 265 people infected in Malaysia died.

The strain in Bangladesh appears to be even more virulent, says Dobson. It kills about 75 percent of the people it infects and jumps directly to them from bats.

Dobson thinks that Nipah outbreaks occur frequently throughout the bat's range, which extends from the Himalayas to Australia. Usually, the illness is "just recorded as encephalitis," he speculates. Fruit bats also carry a related virus, Hendra, which has caused three small outbreaks in Australia since 1994.

Lack of knowledge about bats as viral reservoirs hampers disease research and prevention, says Dobson. "It's really disconcerting, because so many scary emerging and reemerging diseases, including Nipah, Hendra, SAILS, Ebola, and rabies, have bats as their origin. The key question is why do so many of these infections cause no pathology in bats but when they switch to humans cause disease?"

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