While some health officials warn the slaughter of civets could destroy important clues about how the virus is transmitted, some wildlife conservationists charge that eliminating whole species may actually destroy natural buffers to the spread of viruses between animals and humans.

They warn that infectious and previously unknown diseases will continue to proliferate as human populations expand and venture further into wild habitats. Instead of vilifying wildlife and eliminating species, the conservationists say, the focus should be on preventing transmissions.

"It is becoming clear that the majority of emerging infectious diseases can be attributed to human activities that impact natural ecosystems," said Jonathan Epstein, a veterinarian and wildlife epidemiologist at the Wildlife Trusts Consortium for Conservation Medicine in Palisades, New York. "There are so many potentially dangerous pathogens in wildlife that we don't yet know about, and we need to consider this whenever we expand human settlement into pristine habitat, or move wildlife around the world as part of our global trade."

Identifying the Reservoir

SARS, a form of atypical pneumonia, first broke out in Guangdong province in southern China in November 2002. It infected more than 8,000 people and killed 774 around the world before it was brought under control in June last year.

Almost three weeks ago, a 32-year-old freelance television producer was hospitalized in Guangdong with an ailment that was later confirmed to be SARS. Health officials described his case as mild. On Thursday, he was released from hospital.

But on Thursday, the Chinese news agency Xinhua reported a second suspected case of SARS: a waitress in China's southern city of Guangzhou.

When SARS first broke out, scientists quickly identified it as a coronavirus and said it was probably transmitted to humans by an animal. In May last year, researchers from the University of Hong Kong examined 25 animals from eight species in a live animal market in southern China, and found a SARS-like virus in all six civet cats they sampled, as well as in a badger and a raccoon dog.

But a study by scientists from the China Agricultural University later failed to find evidence to link the civet cats to the disease. The World Health Organization maintains that no definite link has been established, and the TV producer who fell ill with SARS is not believed to have been exposed to civets or any other wild animals.

"We think civet cats are involved in the transmission of SARS, but we can't say if the virus jumps from civets to humans or if another animal is involved," Klaus Stöhr, who coordinated WHO's SARS program and now heads the WHO global influenza program, said in a telephone interview from Geneva, Switzerland.

Stöhr says the slaughter of the civets held in captivity is probably necessary, but he warns that reckless culling may eliminate evidence of the origins of the disease.

"The culling may contribute to reducing the risk of SARS transmissions," he said. "But it should not be the only method taken, and it may not even be the most effective way. We need to find out what role these animals play in transmitting the virus. What if we kill all these animals and the virus returns? What animals are we going to kill then?"

Scapegoating Civets

Chinese officials, however, are not taking any risks. On Wednesday, according to the Associated Press, animal merchants in Guangzhou watched aghast as government SARS fighters descended on China's largest wildlife market, and hauled off bagfuls of squirming civet cats for slaughter.

The Chinese government says it plans to kill 10,000 civet cats held in captivity before Saturday, before extending the culling to wild civets and other species, including rats.

Wildlife conservationists call the action short-sighted.

"They're scapegoating the animals," said Barry Kent MacKay, the Canadian representative for the Animal Protection Institute in Sacramento, California. "They're looking for something where they can say, 'We've done this, and it's now OK.' But this does not address the real problem: the trade in and use of wildlife species for food."

Experts say China's unhygienic wildlife markets are fertile breeding grounds for dangerous new viruses. The civet cat is seen as a delicacy in southern China. It's one of the main ingredients in the exotic wildlife dish "dragon-tiger-phoenix soup," for which wealthy Chinese will pay a lot of money.

China banned trade in civets and 53 other wild animals in April last year amid sweeping efforts to stop the spread of SARS. But that prohibition was lifted a few months later despite warnings by scientists that animals might still be a health threat.

"Diseases such as SARS, HIV/AIDS, and monkeypox emerged because we increased our contact with wild animals by moving into their habitat, using them as food, or transporting them as part of a global pet and food trade," said Epstein.

Intensive livestock farming next to the Malaysian rain forest saw the emergence of the deadly Nipah virus in 1999.

Awakening Viruses

Some conservationists have also argued that a greater diversity of species serves as a buffer to the spread of infectious diseases, such as the West Nile and Hanta viruses.

Some animal species are less efficient at producing and transmitting the organisms that cause disease, while others are very good at it. By eliminating species that can get infected but don't transmit the virus very well, while leaving species that are better able to transmit the disease, the risk of transmission to humans may actually increase.

"It's possible the same coronavirus that causes SARS may be carried by animals other than civet cats," said Epstein. "These animals may be better able to transmit disease and so by eradicating civets, according to this theory, we may potentially increase the risk for human infection."

Epstein believes emphasis should be placed on preventing disease exposure and transmission. Simple steps, like excluding wildlife from farms and using fences and screens, can help prevent disease transmission to domestic animals and even humans.

Meanwhile, MacKay, who lives near Toronto and experienced SARS first hand when the epidemic jumped from Asia to Canada last spring, warns of a ticking time bomb.

"We have this nightmare scenario hovering in Asia," he said. "New, infectious diseases could hit anywhere on Earth. Last time it was Toronto, but it could have been San Francisco or any other city. It takes only one infectious person to spread it around."

Michael Lai, a molecular microbiology professor at the University of Southern California in Los Angeles, agrees.

"There is no question that there will be more and more new viruses in the future as we encroach upon wildlife habitat," said Lai. "The viruses we know today probably represent only a small fraction of the viruses existing in nature. We certainly have not seen the end of the story yet, and we need to learn to co-exist with these viruses."