New clues emerged yesterday in the international hunt for the cause of a deadly pneumonia-like illness that surfaced in Asia and has spread to as many as 10 countries, including the United States.
Investigators have traced seven cases of severe acute respiratory syndrome, or SARS, to a single Hong Kong hotel. They have also uncovered more evidence that a common respiratory virus might be the mystery agent behind the disease.
"There's a lot we still don't know," Dr. Julie Gerberding, director of the Atlanta-based Centers for Disease Control and Prevention, cautioned at a news briefing yesterday.
The illness has sickened at least 264 people worldwide and killed nine, according to the latest World Health Organization tally.
Most cases have been in Hong Kong, Singapore and Vietnam. But U.S. officials confirmed yesterday that they are investigating 11 suspected cases in this country. None is in Maryland, according to the state Department of Health and Mental Hygiene.
In Hong Kong, investigators said seven people with the illness stayed on or visited the ninth floor of the 487-room Metropole Hotel - a clue that might help investigators better understand how the disease spreads.
Until that finding, the spread of identifiable SARS cases had been largely limited to families of victims and health care workers who treated them. That led health officials to theorize that the disease was spread only through close contact and by airborne droplets released when people sneeze or cough.
But the new discovery might challenge those early assumptions.
The seven victims - three Singaporeans, two Canadians, a Hong Kong resident and a mainland Chinese who later died - stayed in the hotel between Feb. 12 and March 2, according to Dr. Margaret Chan, director of the Hong Kong Department of Health.
At least two of the victims had direct contact, but information about interactions among the others remains sketchy. No hotel workers have come down with the illness, officials said.
As epidemiologists reconstruct the movements of the victims, investigators analyzing sputum, blood and tissue samples from infected patients have found tantalizing clues about the source of the illness.
On Tuesday, German scientists peering through powerful electron microscopes at nasal swabs from two victims there discovered evidence of a paramyxovirus, a family of microbes that causes mumps, measles, infant croup and other respiratory ailments.
Hong Kong scientists announced yesterday that the same type of virus had turned up in a SARS patient there.
Investigators caution, however, that it is too soon to narrow the search to one agent.
One reason for doubt is that paramyxoviruses were found only in victims' nasal discharges and not in the lungs or other tissues directly affected by the disease. That means the microbes, which are relatively common, could be present in the SARS victims by chance.
Also, the scientists' main tool, an electron microscope, can determine only a virus' general family. Conclusive DNA tests are not yet complete.
Other infectious-disease experts said another virus or bacteria could be causing the illness.
In addition to identifying the cause of the illness, scientists are eager to determine its source. Therefore, discovery of the paramyxovirus in three cases might be important.
Because the microbe also infects wild and domestic animals such as bats, snakes, pigs and cows, scientists said it's possible the disease jumped from animals to humans.
SARS might have surfaced last fall in the Guangdong province of China, a subtropical, agricultural area that previously reported unusual illnesses. Three-hundred cases of "atypical pneumonia" were identified in Guangdong in the fall, resulting in five deaths, but the WHO has not officially included those in its current SARS tallies.
As the illness began to turn up elsewhere in Asia, the WHO issued a global health alert last weekend, its first in a decade.
The symptoms - high fever, coughing and difficulty breathing - are common with many respiratory ailments. Officials said people who experience those symptoms should be concerned only if they have traveled to areas in Asia where the SARS outbreak has been centered.