U.S. health officials say evidence is growing that a previously unknown coronavirus is causing the new form of pneumonia, called SARS, spreading globally from China. The officials would like tissue samples from Chinese SARS patients to help confirm the virus.
The U.S. government's disease tracking agency, the Centers for Disease Control, says blood tests it recently developed show that the coronavirus is present in many patients who suffer from the Severe Acute Respiratory Syndrome.
CDC director Julie Gerberding says this is not proof that the virus causes SARS, but is strong evidence.
"It takes thousands and thousands of samples in people who do or do not have the disease before we can give accurate estimates of how valid the test is in any given person," she said. "What we are seeing so far is that the people who have the strongest epidemiological link to SARS are turning out to have positive tests."
This means that the CDC is finding the coronavirus in people with SARS symptoms, such as fever, cough, and breathing difficulty, and who have been in Asian regions where the incidence of the disease is high. But Dr. Gerberding says her laboratory has not yet performed enough tests to link the virus to SARS for sure.
She points out that the best evidence of a connection is if the coronavirus appears in lung tissue, the key organ infected by the disease. "We have seen coronavirus in some lung tissues, but we would like to know for sure that it is in all the tissues or that we find some indication that it has been there," she said.
As the CDC analyzes more SARS patient tissues, Dr. Gerberding says it would like to have samples from China's Guangdong Province, where the growing epidemic is thought to have originated," she said. "Until now, that has not been possible because Chinese officials have delayed a vist by World Health Organization doctors. They have relented, however, and the team will arrive in Guangdong soon."
Dr. Gerberding says tissue samples from the province are important. "We would, of course, like to share tissue samples or serum [blood] samples of the affected patients, but we do not yet have any samples from Guangdong and I'm not sure anybody has those samples in the collaborating network at this time," she said. "That would be very helpful information, at least to understand what is going on there."
Although the CDC cannot confirm that coronavirus causes SARS, it has enough confidence in a potential link to distribute the virus tests to state health agencies around United States so they can identify possible SARS cases.