Chung-I Wu of the University of Chicago ( an evolution specialist ), helped China's SARS Epidemiology Consortium analyze their findings .
The consortium's research, genetically fingerprinted virus samples from several dozen infected people and animals from China and Hong Kong.
The work provides more evidence that SARS jumps from animals to humans, possibly frequently. And it suggests, that prompt control of new cases is crucial, before viral strains have much time to adapt to people.
Severe acute respiratory syndrome emerged in southern China in late 2002, and went on to sicken more than 8,000 people worldwide before subsiding last June. In that time, it killed nearly 800 people. Civet cats, mongoose-like animals that are sold in live food markets in southern China, are the top suspect for first spreading the disease to people. Thousands have been slaughtered as a preventive measure.But scientists don't know whether some other animals, perhaps rodents who live in the same markets, are the ultimate source of SARS and infected both civets and people at the same time.
The new study doesn't shed light on that question.However, it does suggest that the outbreak wasn't caused by a single species jump. Instead, the study says 11 people apparently were independently infected in the Pearl River Delta area of Guangdong Province beginning in November 2002 -- patients whose virus seems identical to viral samples found in some captive civets.
SARS underwent rapid genetic changes between November and the hospital-based infection, the study found, suggesting the mutations made person-to-person spread easier.
One of those mutated strains came to dominate the outbreak. The Chinese researchers linked that strain's first appearance to a patient who got sick in February -- and whose doctor a few days later traveled to Hong Kong and spread the virus in the Metropole Hotel, the launching pad for global spread.Then, mutations slowed for the remainder of the outbreak.
But last month, China reported the first of three new suspected SARS cases, and that patient was analyzed in the new study, too. His strain is much more similar to SARS found in civets than to any yet-documented human infection.
Specialist's say , " That's not proof a civet infected the man, rather it makes the continual looking for a reservoir host important ."