Traces of the SARS virus have been found in civet cages at a restaurant in China where a person with suspected SARS worked, the World Health Organization has announced.
The finding provides more evidence yet of a widely suspected link between civets and the disease in humans. A WHO inspection team examined the TDL Wildlife Restaurant in Guangzhou city after a 20-year-old waitress fell ill.
Civets, which are related to the mongoose, are eaten as a delicacy in southern China. They are sold in busy food markets, alongside many other animals. However, the role that civets play in transmitting SARS and whether they are the virus’s ultimate reservoir is not yet known. Chinese scientists believe other animals may also be involved, such as rodents.
The first confirmed case of SARS this season, a 32-year-old Guangzhou man named Liu who has now recovered, says he has never eaten or had any contact with civets. But three of the genes from the virus infecting him were a virtually perfect match for SARS viruses isolated in December from civets in the Guangzhou market.
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Both Liu’s virus and the recent civet virus were much more similar to each other than to any strains found in people or animals during the 2003 SARS epidemic.
Zhong Nanshan, head of the Guangzhou Institute for Respiratory Diseases, told a conference in London, UK, on Tuesday that this is strong evidence that civets are spreading the virus. Last week he and other scientists recommended a mass cull of thousands of civets from the market, largely on this basis.
Rat trap
Liu may have caught the virus from a rat he removed from his apartment shortly before falling ill. Ten per cent of the rats in Liu’s building have now been found to carry the virus, says Zhong. But all the civets tested carried it, so Zhong feels they are the ultimate source. “We must stop rearing, selling and eating civets,” he says.
In addition to Liu and the waitress, China has declared one more suspected case of SARS since the end of the 2003 epidemic. That was also in Guangdong province, where the epidemic started.
However, the three patients have suffered fever for fewer days than expected and none of the usual muscle pain and headaches. Furthermore, none has infected their close contacts, suggesting a less virulent SARS strain is to blame.
Nonetheless, the WHO cautions this may simply be due to luck, or to the fact that all three victims are 35 years old or less – SARS is less severe in younger people.
Numerous attempts
Recently published research by virologists at Hong Kong University shows that SARS-like viruses have made numerous attempts to invade humans. The study of 1000 adults from the island shows that two per cent had antibodies to SARS-like viruses in 2001 – more than a year before the first known SARS cases. But none are known to have had SARS-like symptoms.
Other research from Hong Kong, published on Thursday, shows that people’s genes are a significant factor in contracting SARS. The scientists examined variations in genes for human leukocyte antigens (HLA), which are surface proteins on the white blood cells that form a key part of the immune system.
People with one gene variant (HLA-B 0703) were four times more likely to contract the deadly disease than average. In contrast, people with another variant (HLA-DRB1 0301) were more likely to resist SARS infection.
In October 2003, researchers in Taiwan found that another variant (HLA-B*4601) was linked to a raised risk of suffering more life-threatening reactions to SARS.
