The root of SARS still lurks in Asia, and bats may lead us to it. After the deadly virus struck in 2002, disease researchers traced it to raccoonlike animals called Himalayan palm civets, which are sold for food in live-animal markets in China. But when scientists tested civets in the wild or on farms, they found no trace of the disease. The mystery: What other animal carried the virus?
To track down the host, a team from Hong Kong University trapped and tested rodents, monkeys, and bats in the wild. They finally hit pay dirt when Chinese horseshoe bats roosting in water tunnels tested positive. Forty percent had the disease, and a similar number revealed evidence of a brush with the virus. Researchers speculate that SARS may have leapt into civets and then humans, changing its genes slightly each time.
"If this is indeed the ancestral virus of the SARS outbreak, the importance of the work is very high," says virologist Ron Fouchier of Erasmus MC University in the Netherlands. Tracking down the virus's natural host is crucial to halting outbreaks and preventing new ones, he says. Indeed, recent studies show the danger may be greater than previously thought. Researchers at the Guangzhou Institute of Respiratory Diseases say the virus can infiltrate the respiratory tract and also the brain, causing blindness and delirium.
Bats, however, are just part of the puzzle, not its solution. A yet-unknown creature was probably involved—one that may have infected both the bats and the civets. Even so, Fouchier says it would be a mistake to wipe out the bats. The problem is not the bats per se, he says, but rather what humans do with them. The Chinese eat bat meat and use their feces in medicine, he says. "Rather than blaming animals and killing them, we should change our behavior."