GENEVA -- Scientists said Friday they believe they have developed a test for diagnosing the mysterious flu-like illness that has sickened hundreds in Asia -- a crucial step in slowing the disease's spread.

Officials with the World Health Organization said the test still needs further experimenting, but if successful, it should be in the hands of doctors in a few weeks, and available in key laboratories in about seven days.

"We're all very pleased. It is crucial and it's another step on the way, but there's a lot that still has to be done," said Dr. David Heymann, WHO's communicable diseases chief.

Isolating patients

A diagnostic test would make it possible for doctors to quickly weed out and isolate patients with the new disease called severe acute respiratory syndrome, or SARS. It has made 350 people around the world ill and killed 10 people in the past three weeks, according to WHO figures.

Experts suspect it is linked to an earlier outbreak of an unidentified disease in China, where officials say 305 people have fallen ill and five have died.

It is believed to be spread from the nasal fluids of those carrying it -- mostly through sneezing and coughing in close contact.

"What we have now is perhaps a test," said Dr. Klaus Stohr, WHO's chief influenza scientist. "If you are ill and we don't know whether you have SARS or not, we take your blood, we run this test and we know whether you have it or not. But this has to be verified -- double-checked and triple-checked."

Stohr said the virus is being sent to other labs in the network so that the experiments can be repeated and verified.

A network of 11 laboratories in 10 countries, coordinated by WHO, has been working around the clock to try to find the cause of the illness. While it is still not proven, the latest findings indicate a virus is at play.

The development of the test involved isolating the germ from a sick patient and mixing it with blood from recovered patients.

"The blood from the SARS patients kills the virus, which means the virus was previously in these people and now they have antibodies that kill the virus," said Stohr.