Two more studies provide additional evidence that a new virus causes Severe Acute Respiratory Syndrome, or SARS. But the director of the U.S. Centers for Disease Control and Prevention cautions that, while scientists are closing in on the causes of the disease, they are far from a cure.

The two studies are among the first independent reports to back up what the CDC suggested late last month, that a new member of the coronavirus family is responsible for the sometimes-deadly pneumonia called SARS.

Coronaviruses usually cause nothing worse than the common cold. But reserchers in nine countries on three continents found the new virus in SARS patients.

Their two studies appeared online Thursday in The New England Journal of Medicine. Another study published earlier this week in the British medical journal, the Lancet, reported similar findings.

But at a telephone press conference Thursday, CDC Director Julie Gerberding was still cautious. "While we are increasingly confident that we are dealing with a new coronavirus, we can not yet say definitively that this is the cause of SARS," she said.

Dr. Gerberding says researchers still need more tests to have a definitive answer.

And treatment is still a long ways off. She says preliminary test tube studies with the antiviral drug ribavirin were disappointing. Dr. Gerberding says there are other experimental drugs to study.

"And that could lead to a treatment, but it's a ways off, and I don't think we should hang our hat that that's going to be the way we contain the problem, at least in the stage we're in right now," she said.

And, she adds a vaccine is at the very least a year away.

Dr. Gerberding says it may seem like progress in the SARS investigation is slow.

"But keep in mind that this is really just 30 days since CDC activated its emergency response center and began to receive virus specimens. So this is actually an amazing achievement that our laboratories and other international laboratories are even this far along right now," she said.

Other public health experts agree it's unusual to have identified the likely cause of a new disease so quickly.