Scientists investigating the severe acute respiratory syndrome (Sars) virus believe they have solved the mystery of its origin after tracing it to the civet cat, a wild animal that is regarded as a delicacy in southern China.
Investigations into a range of farm and domestic animals in the region over the past month had failed to disclose the virus until it turned up in several animals belonging to a sub- species of the cat.
The finding, if confirmed, will help prevent further outbreaks of the disease if the Chinese authorities use the discovery to impose tougher controls on the farming, sale and slaughter of the animals.
The virus has also been found in the faeces of one raccoon dog, a member of the dog family native to eastern Asia. Antibodies against the virus were also found in the dog and in a badger that was examined.
The sale and consumption of endangered species in China is illegal, but the law is widely flouted. As well as being eaten, the pungent smelling civet is valued for its glandular extracts, which are used in the perfume industry, and for its fur.
Professor Yuen Kwok-yung, the head of the department of microbiology at the University of Hong Kong, who announced the discovery yesterday, said: "From genetic information, it is highly likely that the virus jumped from civet cats to humans."
Professor Yuen said civet cats carried huge amounts of the virus in their stools and respiratory secretions but remained unaffected themselves. This is an important sign that they are the reservoir of the virus and have not merely been infected by another animal.
He called for stringent monitoring of the civet cat trade to prevent more outbreaks. "During the process of rearing, slaughtering or even during the process of cooking the animals, there may be cross-contamination of a lot of items and a lot of surfaces," he said.
Professor Yuen said scientists had isolated four virus samples from the faeces and respiratory secretions of the cats and they were "very similar" to the coronavirus found in Sars patients.
The civet cat belongs to a large group of mostly nocturnal mammals that also includes the mongoose. They are not true cats, but are related to the cat family.
The announcement of the discovery came as the World Health Organisation lifted its travel ban on Hong Kong and China's Guangdong province. The news was greeted with relief in Hong Kong, where the economy has been severely hit by the ban imposed on 2 April. The rate of daily new infections in the territory has remained in single figures for the past 20 days.
Sars has infected more than 8,000 people and caused almost 700 deaths worldwide since it was first recognised in February. The cause of the highly infectious disease, which has spread to 28 countries, was identified two months ago as a member of the coronavirus family - a cause of the common cold - that had never been seen before in humans.
Scientists said then that the virus had probably jumped the species barrier from animals to humans before mutating to become transmissible from human to human. Suspicion initially fell on animals in close contact with human populations in Guangdong, where Sars is thought to have originated in November, including chickens, ducks, pigs and cows.
Professor Ian Jones of the School of Animal and Microbial Science at the University of Reading welcomed yesterday's announcement that the animal source had been found. "It looks very encouraging," he said. "It is the first claim and it will need to be followed by confirmation through sequencing of the virus from that animal."Reuse content