Scientists say they have identified the virus which causes the mysterious, flu-like illness Severe Acute Respiratory Syndrome.

Scientists say the corona virus, now identified as the cause of SARS, is part of the same family of viruses that causes the common cold. But they say it is part of a distinct sub-group of corona viruses that do not have the same properties as the ordinary cold.

World Health Organization virologist Klaus Stohr said that with the identification of this corona virus, it could now be possible to develop more specific diagnostic tests for the disease.

"Now the research can be focused on this virus. The research will help us to develop new drugs," he said. "Now we can focus on one pathogen which has been sequenced, which provides additional information for the development of tests. Now, one can perhaps think about a vaccine if the need be. We are still, I think, optimistic that we can control the disease with the measures which have been implemented."

SARS is spread by droplets through close personal contact. Symptoms include high fever, a dry cough and shortness of breath. About four percent of its victims die. The scientists say this virus has long existed in nature, but it has never been seen in humans before.

They say a new genetic sequencing of the SARS virus proves conclusively that it came from animals. A scientist at the U.S. Center for Disease Control, James Le Duc, says this is the first experience scientists have with this virus. Therefore, he says, a lot remains unknown.

"As you know, it is what we call a virgin soil outbreak," Mr. Le Duc said. "It has never occurred in humans before. How it will progress nobody really knows. But, it is most difficult to control diseases that are spread by droplets in this person-to-person spread. So, I think it would be premature to suggest we are near the end of this outbreak."

The SARS outbreak is most severe in Hong Kong and China, where the disease is believed to have originated. WHO officials report that Beijing has between 100 and 200 cases of the disease, much higher than the official figure of 37.

And, they say up to 1,000 people suspected of being SARS carriers currently are under surveillance. WHO says its experts finally were able to visit military hospitals Tuesday in Beijing. It reports at least 50 patients there are being treated for SARS.