Chinese animals linked to SARS
By Rob Stein
Washington Post
Scientists have discovered the first clue to the origins of the SARS virus, identifying a virtually identical microbe in two small mammals, and possibly a third, that are eaten as delicacies in China.
The findings, announced yesterday, prompted Chinese officials to ban the sale of the animals to try to stem the spread of the disease and prevent new outbreaks, World Health Organization officials said.
While determining the exact role of the animals in the epidemic must await further research, the findings could be a crucial development in the battle against severe acute respiratory syndrome, which has stricken at least 8,117 people and killed at least 689 worldwide.
Discovering the source of the virus would be critical for determining how the infection arose. It could also allow health authorities to eradicate reservoirs in nature where the virus could hide, and from there re-emerge, if the human infections are wiped out. That could allow the illness to be eradicated.
"We believe the window is still open to eradicate this disease," said Klaus Stohr, WHO's top SARS scientist. "It is wider now that we may have pinpointed the animal reservoir."
The long-sought discovery came when a team of researchers from the University of Hong Kong and the Chinese government tested 25 animals from eight species being sold at a live animal market in the province of Guangdong, where the disease first emerged.
The tests found a virus that appeared virtually identical to the SARS virus in saliva and feces of six catlike animals, known as masked palm civets. Tests also showed genetic evidence of the virus in feces of another animal, known as a raccoon dog, and an eighth animal, a Chinese ferret badger, had antibodies to the virus in its blood. None of the animals was sick.
A detailed genetic analysis of the virus isolated from the animals found it was identical to the SARS virus from human patients except that it lacked one sequence. The missing genetic material carries instructions for the production of a small protein, known as a peptide, and may have been the change that allowed the virus to jump to humans and then spread readily, Stohr said.
"The lack of this peptide may have helped the virus transmit efficiently from human to human," Stohr said. "Perhaps that missing piece of protein is just the trick, the little difference between a harmless animal virus and a human pathogen. That's a bit of speculation, but this is one hypothesis."
The civets appear to be the most likely candidates, since the virus was found in more of those animals than any other. In addition, China apparently began importing the animals in significant numbers from Vietnam within the past year, Stohr said.
"That would fit with the occurrence of this disease," he said.
Civets are nocturnal creatures related to the mongoose. They resemble small raccoons or weasels and have become prized by chefs at pricey restaurants.
There are many unanswered questions, Stohr said. It is unknown whether the animals were trapped in the wild or bred on farms. It is also unknown whether the animals came to the market infected or became infected on arrival.
"What these findings mean is that the SARS coronavirus exists outside humans," Stohr said. "It's being excreted in certain amounts in animal species. That means there's a public health risk and that someone dealing with these animals or handling them could become infected."
If the animals are spreading the virus, it is more likely occurring when they are handled or slaughtered, and not when they are eaten, because cooking would kill the virus, Stohr said.
"If this virus is as widespread as this small-scale study would suggest, it would suggest that the public health risk is not localized, but that it's practically everywhere," he added. "We know these animal markets exist in many places in China."
