- The Washington Times - Tuesday, May 20, 2003

Recently, more than 48,000 people showed up in Toronto to watch the home town Blue Jays play the Texas Rangers in an American League baseball game. While ticket sales no doubt were helped by a $1 per seat promotion, the large crowd also was a result of the World Health Organization’s decision to the lift its travel advisory to the city. The good news in Canada today is that SARS — severe acute respiratory syndrome — appears to be under control.

The news is not as good throughout the world. By latest count, more than 7,600 SARS cases have been reported around the globe, with more than 580 deaths. More than 25 nations are now battling the SARS epidemic. And health officials maintain that SARS could easily recur even in regions that appear under control.

In mid-April, researchers concluded that a new pathogen, a member of the coronavirus family never before seen in humans, is the cause of SARS. Other pathogens within the coronavirus were first isolated and described in the 1960s from respiratory secretions in adults with the common cold.

With that knowledge, global health officials are now placing considerable attention toward the development of a SARS vaccine. While these efforts should continue, it is important to remember that similar endeavors in the past toward a vaccine for the common cold have not proved viable. Thus, more immediate returns may be obtained from studying exposure routes and methods to reduce the risk of exposure. This type of data can lead to approaches for control that can be implemented easily and rapidly.

What can we learn bout this emerging virus from the research gained from studying other coronavirus pathogens? We know that most viruses have a low infectious dose, which means that only a few are needed to begin an infection. Coronavirus is thought to spread primarily through person-to-person transmission. Coronaviruses as well as the SARS virus have been found in fecal material. These viruses can live on surfaces, in one study, as long as six days and environmental transmission is possible.

Risk of transmission or the likelihood of becoming infected is defined by many factors — the numbers of viruses, the viability and survival of the viruses, and the levels it may take to initiate the infection given the route of exposure. In lay terms, exposure directly to the virus from a sneeze or contaminated hands from one person to another may be associated with the greatest risk. Through person-to-person transmission, an individual would be exposed to greater numbers of live virus. Lesser risks would be associated with contact through surfaces or materials. However, the level of the risk reduction and the potential for transmission has not been quantified.

We also know that airborne human coronavirus is more likely to survive in colder temperatures. As such and alarmingly, health officials are bracing for an increase in SARS cases in the fall. And finally, research has shown that certain chemical disinfectants (but not all) can be effective in killing coronavirus on various surfaces.

A simple Google search will turn up numerous products that purportedly protect against SARS — masks, air filters, hand gels, disinfectants, diet supplements, colloids, etc. The public should not rush off to purchase these products. We simply do not know enough about exposure transmissions. We also have not decided what the safety goal for protection for these products should be.

But there are simple preventive measures the public should employ. First and foremost, we should frequently wash our hands with soap and water — the foundation of good hygiene. In addition, proper disinfection of surfaces — particularly in healthcare settings, but also in the home — can help ward off most germs and viruses. In fact, in an encouraging step announced this past weekend, WHO concluded that SARS loses infectivity after exposure to different commonly used disinfectants, such as chlorine bleach.

Though hand washing and disinfection are hallmarks of public heath protection, it is important to remember that these measures have not been fully tested against the SARS virus. Therefore, as the global health community races to develop a SARS vaccine, it must equally invest in understanding exposure. Experts believe a vaccine can be developed in one to three years, an optimistic timetable. But without more knowledge on exposure routes, one to three years will be too long.

Joan B. Rose, a microbiologist, is the Homer Nowlin Chair in Water Research at Michigan State University.


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