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Last Updated

18 May 2003

Source: New York Times, May 18, 2003

W.H.O. Scientists Say Tactics to Fight SARS Are Working


Scientists brought together by the World Health Organization to review the data on SARS said yesterday that existing public health measures had been effective in containing the disease in many countries and should work eventually in China and Taiwan, where SARS is now concentrated.

Crucial measures that have broken the chain of person-to-person transmission of the SARS virus are the detection and treatment of suspected cases as soon as they are identified and then quarantining their contacts. The measures also include providing timely public information and alerts to travelers.

The message of the two-day meeting, which took place in Geneva but was joined by scientists from around the world by videoconference, was of "great hope, one of celebration that the measures are working, but also a call to action because we've got a lot more to do yet before we end this problem," said Dr. Michael J. Ryan, an official of the health agency.

Although the virus that causes SARS, or severe acute respiratory syndrome, has occasionally been found on animals and on a cockroach, there is no evidence that animals or insects are spreading it, said one participant, Dr. Arlene King of Health Canada. Nor is there any sign that infected individuals are spreading the virus before they become ill.

Another participant, Dr. Margaret Chan, Hong Kong's health director, said findings from a study to be issued this week reinforced the importance of people's seeking early medical attention. Detecting and isolating patients early in the course of their infection and quarantining their contacts has had a huge effect on slowing the spread of the outbreak, Dr. Chan said. Her department conducted the study with researchers from Imperial College in London.

But Dr. Chan also said the recommended public health measures need to be kept at least another year wherever transmission seems to have stopped to be sure that the virus is not hiding, ready to strike again.

An earlier study from Imperial College suggested that the period between exposure to the virus and the onset of symptoms might be about four days longer than the current upper limit of 10 days. The consensus of the participants was that the 10-day incubation period was correct but that epidemiologists needed to study further the few cases that exceeded that limit.

Information at the meeting affirmed that SARS is spread principally by droplets dispersed in coughs and sneezes among people with close and sustained contact with an infected individual.

Although people with the disease seem most infectious in the second week of their illness, health officials have to treat all cases as highly infectious from the start of symptoms to minimize the spread of the virus, said Angus Nicoll of Britain's Health Protection Agency.

New information was helping scientists learn more about a small number of individuals, called super-spreaders, who have transmitted the virus to scores of other people, the participants said.

It is important to distinguish between a super-spreader and a super-spreading setting, Dr. Chan said, and that is a very complex epidemiologic and environmental problem. Among the determinants are the amount of virus an individual can transmit and the settings in hospitals and elsewhere that allow close contact with many other individuals.

Dr. Ryan said that many super-spreaders had numerous opportunities to spread the virus because they had spent a long time in the community while ill or because hospital staff had not used the proper infection control measures.

Some evidence suggested that contaminated feces and urine could contribute to the spread of SARS if they became dispersed in droplets in the air and the droplets could be inhaled or swallowed. But that route is not a major means of spreading the disease, Dr. Ryan said by telephone in a news conference after the meeting in Geneva.

Canadian environmental scientists invited by Hong Kong and the World Health Organization to investigate a large outbreak of SARS in an apartment complex in Hong Kong concurred with earlier findings by scientists there, Dr. Chan said. She said that the Hong Kong and Canadian investigators found that a collection of factors had to converge to cause the outbreak. They included: an infected individual who transmitted the illness to a dozen or so other people living in one line of apartments in the complex, diarrhea developing in at least one of the infected, and a malfunctioning of the plumbing and sewage systems.

Dr. Ryan said the SARS epidemic in China consisted of multiple outbreaks in different areas. As Chinese health officials get better data on the epidemic there, they are applying the important lessons of infection control learned in other countries. But the benefit of the health measures that are beginning to be put in place now will only be apparent in another few weeks, he said.

W.H.O. officials have said that in many recent suspected SARS cases, Chinese health officials have not been able to identify the individual from whom a new case caught the infection. There are many potential explanations for that situation. One is that another respiratory illness caused by a different infectious agent had occurred simultaneously. The para-influenza virus is one that health officials are investigating as a possibility.

Dr. Chan said that when her department first confronted SARS in Hong Kong, "we had no idea what we were dealing with and we did not even know it was a virus." But Dr. Chan said the experience taught health officials not to "be afraid to say you don't know what you are dealing with."

"SARS is too big for any country to handle single-handedly," Dr. Chan said. "It calls for regional and global collaboration, and the collaboration has been unprecedented in terms of identifying the virus" and carrying out other research. The W.H.O. has been widely praised for organizing teams of laboratory scientists, epidemiologists and health officials around the world immediately after it declared SARS a global health risk on March 12.

"All in all, we have more success stories than mistakes," Dr. Chan said.

Yesterday, the agency added China's Hebei province to its list of places that people without urgent business should avoid. The other areas are Taiwan, Hong Kong and Beijing, Tianjin, Inner Mongolia and Shanxi and Guangdong provinces in China.