Scientists unlocking SARS secrets

MARCH 31–WINNIPEG–Scientists in Hong Kong and the United States say they are honing in on the virus that causes severe acute respiratory syndrome (SARS), saying they will soon have a rapid test to detect infections.

But one of Canada’s leading experts on infectious disease told Canada’s Globe and Mail that it is too soon to say that the puzzle has been solved.

“We have made considerable progress, but we don’t have the answer yet,” says Frank Plummer, scientific director at the National Microbiology Laboratory in Winnipeg.

Researchers are focusing on two infectious agents: a new coronavirus (a crowned-shaped virus that usually causes colds) and a metapneumovirus (from a family of viruses that usually cause respiratory ailments in children).

“We’re finding evidence of both infectious agents,” Plummer said.

The key unknown, he said, is whether one of the viruses is the cause of severe acute respiratory syndrome and the other is coming along for the ride, or if it is necessary for both pathogens to be present to trigger serious illness.

Plummer said scientists also need to keep their mind open to the fact that SARS may also be caused by other, as-yet-undiscovered infectious agents, and the presence of the other two viruses is coincidental.

Microbiologists from the University of Hong Kong say that SARS is definitely caused by a new strain of coronavirus, one that is similar to a virus found in cattle. They renamed the disease coronavirus pneumonia, or CVP.

The U.S. Centers for Disease Control and Prevention has also identified the same coronavirus as a possible cause, but is keeping an open mind, noting that research elsewhere in Hong Kong and in Canada points to the metapneumovirus.

“The evidence in favour of this illness being caused by a previously unrecognized virus in a group of viruses called coronaviruses continues to mount,” said Jim Hughes, head of the infectious disease branch at the CDC. “I am not ready to say it is definitive evidence yet.”

Worldwide, there are at least 1,408 SARS cases, including 53 deaths. The numbers jumped dramatically on Wednesday when Chinese health officials finally confirmed that a mystery disease outbreak late last year was SARS.

The outbreak in China began in November, but the origin of the disease is unclear. The cases outside mainland China, including those in Canada, seem to originate with a doctor from China’s Guangdong province, who transmitted it to seven people who visited the ninth floor of the Metropole Hotel in Hong Kong, where he stayed in late February.

SARS usually begins with a high fever, chills, muscle aches and a dry cough. After about a week of mild illness, patients can go in one of two directions: The majority begin to show improvement without any specific therapy. But 10-20 per cent of those infected develop serious respiratory problems, including pneumonia. To date, about 4 per cent of those infected have died.


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