for National Geographic News
For a virulent virus seeking to jump from animals to humans China's Guangdong province may be the perfect habitat.
Along the highways, ubiquitous farms are lined up next to each other, with farmers tending their ducks, chickens, and pigs in teeming and cramped quarters. In the city's food stalls, meanwhile, vendors keep their meatalive and deadin cages and baskets stacked on top of each other. Customers can choose from a menu of rats, cats, dogs, frogs, snakes, and exotic birds.
In such unhygienic conditions, scientists have long warned, it's just a matter of time before a hidden and potentially lethal virus would make the leap from animal to man. It should come as no surprise, then, that one virusthe enigmatic coronavirus that causes severe acute respiratory syndrome, or SARSin all likelihood did.
Among the first people to die from SARS, when the epidemic began in the southern Guangdong province late last year, were food handlers. Since then, at least 6,583 people in 30 countries have been infected with SARS. As of yesterday, the disease has claimed at least 461 lives.
China has an unfortunate history of producing new viral strains. Two devastating influenza pandemics, in 1957 and 1968, both originated in China, each killing more than a million people. Experts maintain that outdated farming practices, overpopulation, and even political secrecy may be to blame.
"China is the perfect breeding ground for new viruses," said Christoph Scholtissek, a German virologist whose research has linked China's traditional farming system with the emergence of lethal human viruses.
Although researchers havein record timemanaged to crack the genetic make-up of SARS, the mysterious virus doesn't match any known animal or human viruses. In other words, scientists still don't know the source of SARS.
Many emerging infections already exist in nature. They may enter humans as a result of changed ecological or environmental conditions that place humans in contact with previously inaccessible pathogens or the natural hosts that carry them.
"The most likely scenario is that [SARS] has been circulating in another species in southern China, and human beings came in contact with it this past autumn," said Stephen Morse, an epidemiologist at Columbia University in New York and author of Emerging Viruses.
Known as "zoonosis", the virus transfer from animals to humans has long been established. Foreign microbes can be lethal because the new host may not have the immunity that has built up over time in the original species.
Some virologists believe traditional farming practices in China help spread new viruses. Chinese farmers raise ducks, pigs, and fish in one integrated system, and the animals may exchange viruses through their feces.
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