January 30 2004 at 05:54AM
By Maggie Fox
Washington - The Severe Acute Respiratory Syndrome (SARS) virus fine-tuned itself to become more infectious as last year's epidemic spread across China, researchers reported on Thursday.
Early patients with SARS had a genetically form, very similar to that seen in civets, while the last patients in the epidemic had a slightly mutated form, the researchers said.
"What we see is the virus fine-tuning itself to enhance its access to a new host, humans," Chung-I Wu, a professor and chairperson of ecology and evolution at the University of Chicago, said in a statement.
'Early patients with SARS had a genetically form' "This is a disturbing process to watch, as the virus improves itself under selective pressure, learning to spread from person to person, then sticking with the version that is most effective."
This may explain why the virus became more infectious with time, Wu said.
The finding, published in the journal Science, supports the idea the virus leapt to people from animals and also should allow experts to understand the virus better.
SARS infected more than 8 000 people last year and killed nearly 800. This year, two people have been confirmed to have been infected with SARS and a third is considered a probable case, all in China.
The virus that causes the disease, marked by severe pneumonia, is a never-before-seen type of coronavirus. Coronaviruses cause the common cold in people and a range of infections in animals.
'SARS infected more than 8 000 people last year' Wu, Guoping Zhao of the Chinese National Human Genome Centre, and colleagues in China including at the Guangdong Centre for Disease Control and Prevention studied the spike protein on the virus, known to give the microbe its ability to infect.
In the first people infected it was virtually identical to viruses taken from civets, weasel-like animals valued for their meat and sold in markets in southern China.
As the virus spread more freely from person to person, it mutated slightly, apparently adapting itself better to live in humans. That was when the "super-spreading" occurred that made the virus so frightening, including the case of a doctor who infected several people at a Hong Kong hotel.
The virus then gradually evolved into a more stable genetic form toward the end of the outbreak, Wu's team reported.
They said the study should help researchers find a vaccine against SARS based on the spike protein.