The bats apparently are carriers of SARS, which caused severe economic losses, particularly in Asia, as it spread to Canada and other countries. In Asia, many people eat bats or use bat feces in traditional medicine for asthma, kidney ailments and general malaise.

The Chinese horseshoe bat does not exist in the United States.

The finding is important in preventing outbreaks of SARS and similar viruses carried by bats because it provides an opportunity for scientists to break the transmission chain.

Two Teams, Similar Findings

One team from China, Australia and the United States reported its findings Thursday in the online version of Science. The other team, from the University of Hong Kong, reported its findings Tuesday in the Proceedings of the National Academy of Sciences.

"It's pretty pleasant to see two teams that did not know each other reach similar findings," Dr. Lin-Fa Wang, a virologist at the Australian Animal Health Laboratory, said in a telephone interview. After collecting hundreds of bats from the wild and from Chinese markets, each team reported identifying different viruses from the coronavirus family that are very closely related to the SARS virus.

SARS, or sudden acute respiratory syndrome, first appeared in China in 2002. It spread widely in early 2003 to infect at least 8,098 people in 26 countries, according to the World Health Organization. The disease died out later in 2003, and no cases have been reported since.

SARS now appears to join a number of other infectious agents that bats can transmit. Over the past decade, bats have been found as the source of two newly discovered human infections caused by the Nipah and Hendra viruses that can produce encephalitis and respiratory disease.

Strong Genetic Evidence

Wang said his group focused on bats largely because of the team members' earlier pioneering work on the Hendra and Nipah viruses. One member, Dr. Jonathan H. Epstein, a veterinary epidemiologist at the Consortium for Conservation Medicine in Manhattan, led the scientists in gathering bats from the wild and marketplaces.

After obtaining fecal and blood samples, the scientists released the bats into the wild or returned them to the markets. The specimens were tested for a variety of viruses that infect animals.

Laboratory analysis of the coronaviruses' makeup provided strong genetic evidence of the relationship between those found in the bats and the SARS virus.

Although it is logical to assume that the bat viruses infected the animals in the live markets to cause the outbreak, the studies were not planned to prove that point.

"The genetic relationships do not tell you anything mechanistically about if or how the virus moved from the bats to civets and from the civets to the humans," said Dr. Donald S. Burke, a virologist and professor at Johns Hopkins.

Better Sanitation, Education

Wang said that "there is no rule" to establish proof that a certain species is the reservoir, or hiding place, of a virus, but that scientists make the judgment based on criteria like how widely the infectious agent is distributed in a species, the absence of symptoms among the animals and finding high levels of antibody but low amounts of virus in the animal.

It was highly unlikely that insects transmitted the SARS viruses to bats, because the viruses do not grow in insect cells in the laboratory, Wang said. Most civets that are sold in China as a delicacy are farmed, Wang said, and the government should make sure civet farms are distant from bat colonies, routinely monitor farmed civets for SARS-like viruses and allow just noninfected animals to be sold in markets.

Also, health workers should improve sanitation in the markets, and educate people about the dangers of mixing bats, civets and other animals there.