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Study Suggests Hygiene Important in Controlling SARS - 2003-08-18

The world continues to see new infections for which there are no vaccines. Severe Acute Respiratory Syndrome is just one of the latest examples, but these diseases are still vulnerable to simple control measures. A new study has found the most deadly enemies of these infections are soap, masks, gowns, and gloves.

Earlier this year, medical workers, scientists, politicians and donors around the world battled to stop the spread of the SARS virus. University of California researcher James Lloyd-Smith and colleagues used mathematics as their weapon to help the fight. They used formulas to search for the most effective ways to halt the SARS epidemic.

They found that protective clothing and hand washing in the hospital are the most important weapons in fighting SARS and other contagious diseases.

"We were pleasantly surprised to find that these simple measures, these hospital-wide infection control measures, had such power," said Mr. Lloyd-Smith. "Simple measures of wearing gloves and masks and gowns - things that all countries can afford - are sufficient to stop an epidemic of SARS, and by extension a similar respiratory-type disease like an influenza outbreak."

In their study, the researchers employed mathematical formulas to simulate the spread of SARS. The factors they used included the effects of different control measures, such as quarantine or simple in-hospital contact precautions, how quickly the sick were hospitalized, and the number of people one individual infected.

The equations show that simple preventive precautions within a hospital, hand washing and wearing protective clothing, were more effective at limiting the number of SARS infections than patient quarantine, going out and finding those whom the infected people had met, and reducing contact between hospital workers and the community.

Not surprisingly, they found that combining all of the containment steps was most effective. But if nothing else was done, protective outfits and hygiene in the hospital could substitute for any other measure, including costly techniques like isolation facilities.

World Health Organization infectious disease specialist Christopher Dye says the study confirms the importance of steps that health workers were taking at the time.

That is often the case in epidemic control," he said. "In many instances, we do not need high technology to control epidemics. What this study does is it gives us some comfort that the recommendations that were made on a rather practical basis, in the first instance, now have even more solid scientific backing."

Why are the simple precautions the best? Because a measure like isolation prevents only the sick from spreading infections. But soap and protective clothing prevent all others from spreading the disease.

Since most SARS cases are in the hospital, Mr. Lloyd-Smith says preventing contact there has the greatest impact. "In the hospital where, for SARS, there is an awful lot of transmission going on, having precautions that apply to everybody who comes in the door catches people whom you have not diagnosed yet," he said. "And they may be spreading a few extra infections, which is just enough to prevent you from getting a cap on the outbreak."

Mr. Lloyd-Smith says renewed outbreaks in Toronto and Taiwan were caused by relaxing simple hospital precautions. Once protective clothing and hygiene were required again, the epidemics were brought under control.

A speedy public health response is also critical to controlling disease. Mr. Lloyd-Smith's research shows that the sooner infected individuals are hospitalized the fewer people they infect. But he says quick action by itself is not enough.

"You really need to understand where the weak link in your current system is in order to best, most efficiently move forward in fighting it. So, for instance, it does not do you any good if you rush to get everyone into the hospital immediately if the infection control procedures in the hospital are not adequate," he said.

The scientific group that published the study, the Royal Society of London, says the findings will help authorities make decisions about how to allocate limited resources in the future.