ATLANTA -- The mysterious and deadly flulike illness from Asia that has stymied health officials around the world appears to be caused by a new variety of a common cold virus, U.S. health officials said Monday.
The head of the U.S. Centers for Disease Control and Prevention said a number of tests had revealed traces of a form of microbe known as a coronavirus in the tissue of people infected with the unidentified disease.
"There's very strong evidence to support coronavirus" as the cause, CDC director Julie Gerberding said. However, she cautioned more testing is needed before experts can be certain.
Many different viruses can cause colds, including three different varieties of the coronavirus. Until now, the cold is the only human ailment known to be caused by coronaviruses, but the CDC said the culprit in the Asian outbreak appears to be genetically different and probably represents a fourth type.
Just what that means for treating severe acute respiratory syndrome, SARS, which has sickened 456 and killed 17 since Feb. 1, is unclear. There are no certain treatments for colds. Nevertheless, Gerberding said the Defense Department will test the virus against all known antiviral drugs to see if any work.
Researchers worry any virus they find in patients might be an innocent bystander.
Among the bits of evidence suggesting the new coronavirus is the cause is the discovery that victims develop an immune system response to it during the course of their illness.
The illness first gained attention in Hong Kong, Singapore and Vietnam, where it has spread among health workers in hospitals. Health authorities say it appears to spread from close contact, primarily through nasal fluids by coughing or sneezing.
Gerberding's announcement followed comments Monday from a WHO scientist who said coronavirus was a possible cause. But the virologist, Dr. Klaus Stohr, continued to give more weight to a different virus, described by WHO officials earlier, the paramyxovirus.
Gerberding said her researchers had not found that virus in their tissue samples.
Fears of the disease seemed to spread in Asian centers. Singapore quarantined more than 700 people who might have been exposed to the disease, threatening them with fines. Hong Kong officials met to draw up health guidelines for everything from restaurants to bus systems in an attempt to slow its spread.
Hong Kong's health secretary, Dr. Yeoh Eng-kiong, called SARS "a really very alarming disease," the likes of which Hong Kong has never seen.