|Stalking SARS: Genomics in a Chinese Marketplace|
By Kate Dalke
September 5, 2003
Where did SARS come from? That’s what scientists have wanted to know ever since severe acute respiratory syndrome emerged in China last spring and then spread to more than 30 other countries.
They still don’t have their answer. But the culprit is presumed to be a novel coronavirus that jumped from animals to humans relatively recently. Among the animals that may have transmitted the virus, the leading suspect is the civet.
Today scientists are reporting that SARS-like viruses isolated from two Himalayan palm civets from a market in Guangdong, China, are similar to SARS viruses isolated from people.
The findings were announced in May, but the details of the study have just been published online in Science.
The scientists sequenced the genomes of SARS-like viruses isolated from the two palm civets and compared them to 11 human SARS viruses.
The animal and human viruses are closely related. The genome sequences are 99.8 percent alike, but with clear differences: the human virus lacks a group of 29 units of DNA.
Food markets in southern China have been at the center of a debate over whether they harbor animals that are reservoirs for the disease. The new study confirms the role that uncontrolled food markets can play in spreading SARS as places where a virus population can expand and be transmitted to new hosts, including humans.
The study was led by Yi Guan of the University of Hong Kong and included other researchers from that university, the Center for Disease Control and Prevention in Shenzhen, Guangdong Province, and the Department of Health in Hong Kong.
The first cases of severe acute respiratory syndrome were found in restaurant workers from Guangdong, who handled exotic animals that are a culinary delicacy in the area.
Chinese authorities banned the sale of certain exotic animals this past spring, but have since lifted this band because of economic pressures.
The research does not provide evidence about a natural reservoir for the disease. It is possible that another animal not yet identified had the virus and passed it to civets and other live animals.
Of the 25 animals tested from the live animal market in Shenzhen, an immune response against the animal virus was seen in the Himalayan palm civets (Paguma larvata), a raccoon-dog (Neyctereutes procyonoides), and a Chinese ferret badger.
Some workers at the same market tested positive for antibodies against the animal virus but none reported any SARS-like symptoms in the last six months. The workers included wild animal traders, those who slaughter the animals, and vegetable traders.
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