Severe Acute Respiratory Syndrome (SARS), like many viruses that have caused widespread outbreaks, is thought to have originated in animals in Southern China. VOA's Katherine Maria talks to a researcher who spent his life tracking the origins of viruses that cause pandemics.
Severe Acute Respiratory Syndrome shares at least one thing with flu pandemics like the 1918 Spanish influenza, which killed more than 20 million people, and the Russian flu of 1977. Both are thought to have originated in the same region of the world: Southern China.
Dr. Graham Laver, a recently retired researcher from Australia's Canberra University, has spent his career tracing viruses.
"In 1918 at the end of World War I, there was the Spanish flu pandemic, which was really very vicious and killed 20 million people," he explained. "The next big epidemic was in 1957, which was Asian flu, which again started in China, and then in 1968, Hong Kong flu came along, and in 1977 Russian flu that also started in China. People who say is China the birthplace of flu have to look at those things. It's a fact. "
A spherically shaped pathogen with tiny spires protruding from its surface has been identified as the virus behind the SARS outbreak.
It is not a flu virus, but belongs instead to the family of coronavirus, named for their crown-like appearance.
Microbiologist KY Yeun of Hong Kong University says this virus likely jumped from animals into human populations.
He and doctors from China's Center for Disease Control found evidence of the virus in civets, which are related to the mongoose, traded in food markets in China's Guangdong Province.
"Looking at the genetic information, it is highly likely the virus has been jumping from the civet to humans," he said.
Dr. Laver is not surprised by the animal link to the SARS outbreak, which has in its first seven months infected more than 8,000 people in about 30 countries.
Back in 1972, Dr. Laver was one of the first to find hard evidence that the Hong Kong flu of 1968 had jumped the "species barrier" from birds to humans. Previous scientific theory held that viruses mutated only within human populations.
"Nobody knew where these new flu viruses came from. The general idea was that they arose by mutation from other viruses," he explained. " From experiments we did in the lab we showed that quite clearly this was wrong. That the new viruses arose from animal or bird viruses… This idea is now accepted by everybody. "
Dr. Laver says there are several theories explaining why many outbreaks originate in China.
One suggests that most humans do not produce antibodies that would protect them from viruses carried by rare, wild animals captured for food in Southern China. The animals do not always show symptoms of sickness, and when humans prepare the animals for eating, humans can become infected with a virus lurking in the host animal.
Dr. Laver points out that domesticated farm animals can also be a source of novel viruses. The H5N1 virus or avian flu, originated in chickens and killed six out of 18 people infected in Hong Kong in 1997.
Other theories point to the close proximity in which animals and humans live in the densely populated farming communities of Southern China. The region's warm, humid climate also favors the growth of microbes.
Dr. Laver says viruses probably originate in China due to a combination of factors promoting ideal conditions for animal to human disease transmission.
Just days after hearing the news that the civet is a likely carrier of SARS, authorities in Guangdong Province started to confiscate wild creatures from markets.
But Dr. KY Yeun says it is not realistic to try to outlaw the trade in wild animals; after all, he says, you cannot wipe out 5,000 Instead, Dr. Yeun suggests that wild species used for food be handled differently or inoculated against known diseases.
"It is very important that we have ways of controlling the rearing, the slaughtering and the selling of these wild game animals so that such epidemics will not occur again," he said.
But inoculating wild animals like the civet against SARS might not prove adequate.
The SARS virus likely jumped from animal to human repeatedly, says Dr. Yeun, but did not cause a serious outbreak until it mutated. The mutation allowed the virus to adapt to humans and to human-to-human transmission.