送交者: skywalker00 于 2005-9-29, 19:57:47:
Scientists Find Initial Host,
Now Look for Ways to Stop
Transmission to Humans
By GAUTAM NAIK
Staff Reporter of THE WALL STREET JOURNAL
September 29, 2005 8:22 p.m.
A team of international scientists has pinpointed bats as the original hosts of the deadly SARS virus, which emerged in southern China in 2002, sickened about 8,000 people and killed more than 700.
The scientists' study suggests severe acute respiratory syndrome is loose in the wild and could re-emerge to infect humans. But there is a practical benefit to the finding: Now that authorities know the original animal host, they can try to interrupt the transmission of the virus before it infects people.
To prevent another SARS outbreak, said Peter Daszak, an author of the study, the Chinese must "cut down the use of this bat for food and medicine." Dr. Daszak is executive director of the Consortium for Conservation Medicine, a group of five scientific organizations. The group's paper was published yesterday on the Web site of the journal Science.
But Klaus Stohr, a virologist at the World Health Organization in Geneva, cautioned that, while the finding was important, many questions remain. For example, it is unclear how long the virus stays in bats or what specific genetic changes it undergoes. Nor is it known whether the virus found in bats must infect intermediate animal species before jumping to people. "It takes us one step closer to the chain of events" that led to the human SARS outbreak, said Dr. Stohr. "But we're not there yet."
SARS is a viral respiratory illness. Starting in 2002, it spread to more than two dozen countries in Asia, North America, South America and Europe before the outbreak was contained.
Early research had suggested that SARS jumped to people from masked palm civets, which are weasel-like animals. The virus was found in civets being sold in marketplaces. But civets found at farms or in the wild didn't seem to carry the virus, so many scientists were certain that they hadn't discovered the original host of the virus. In September, scientists reported the discovery of a SARS-like virus in Hong Kong bats. The latest study amplifies that finding and strongly indicates that the original SARS host was the horseshoe bat, which is eaten and used for traditional medicine in China. The latest research studied a larger number of animal samples than the previous one, and focused on several sites in mainland China, including the place where SARS emerged.
Dr. Daszak's group homed in on bats because they are known to harbor a host of lethal germs and are a common part of the wildlife trade in Asia. The team tested more than 400 bats, representing nine species, from four locations in China. Virus samples taken from the bats were found to be 92% to 94% genetically similar to the virus that sickened people, the research showed.
Each time a virus jumps from one species to another, it undergoes a small genetic change. By studying the sequence of such changes backward in time, scientists can get a good fix on how the virus leaps from one animal to another.
The Consortium for Conservation Medicine is based at Wildlife Trust, an international conservation group. The consortium consists of the Cummings School of Veterinary Medicine at Tufts University, Harvard University's Center for Global Health and the Environment, Johns Hopkins Bloomberg School of Public Health and the U.S. Geological Service's National Wildlife Health Center and Wildlife Trust.