April 06, 2003
Scientists Say SARS Spread May Be Inevitable

Experts in public health and infectious disease are beginning to say that they believe SARS is more likely to spread to pandemic levels than to be contained.

"Most people are hesitant to say it will just go away," said Dr. Ruth Berkelman, head of Emory University's Center for Public Health Preparedness and Research. "Too many people are infected to think we won't see it for a long time to come."

In an editorial in The New England Journal of Medicine US CDC Director Dr. Julie Gerberding thinks it would require extreme luck for SARS to be controlled.

"If we are extremely lucky, the epidemic will be curtailed, develop a seasonal pattern that will improve prospects for regional containment, or evolve more slowly than it has at this early stage," Julie Gerberding, director of the U.S. Centers for Disease Control and Prevention, wrote in an article this week.

"If the virus moves faster than our scientific, communications and control capacities, we could be in for a long, difficult race."

Note that her extreme luck scenario is for SARS to be controlled, not eliminated.

Dr. Donald Low (who is currently in isolation having himself been exposed to SARS) thinks SARS will become pandemic (i.e. widely spread).

"Unfortunately, it's an epidemic now that will become a pandemic," predicted Donald Low, chief microbiologist at Toronto's Mount Sinai Hospital.

Dr. David Heymann of the World Health Organization thinks we won't know whether we can contain SARS until we have a reliable test for infection.

"I think we've got to keep going at this speed until we get that diagnostic kit in use and figure out what's going on," Heymann said. "Then we'll know if we've lost or not."

One reason for the increased pessimism is the growing belief that some SARS sufferers are high infectious "super spreaders".

The four-member team is most interested in "the phenomenon of 'super spreaders' -- people who seem to spread their disease to a lot of other people," said the WHO team leader, Dr. Robert Breiman.

It is possible that co-infection with another pathogen makes a person into a "super spreader".

"It raises the question of, if you have one pathogen and you get hit with, say, coronavirus . . . are you more likely to transmit? Do you become what we call a 'super spreader?' " Breiman said.

Chinese scientists see evidence in some SARS sufferers of a rare airborne chlamydia bacteria that may be turning people into super spreaders.

Dr Robert Breiman, also of the WHO, said he feared people who already had chlamydia might be vulnerable to the flu-like bug and become highly contagious "super-spreaders".

Governments are moving to increase their quarantine powers. George W. Bush has signed an executive order giving public health officials the legal power to quarantine SARS victims. The Australian government has also moved to grant public health authorities power to force people into quarantine and even to close borders.

It seems likely at this point that decreased travel levels, use of facial surgical masks, and other responses to SARS will be longer lasting and spread to more locales. The economic cost of SARS then seems likely to increase substantially. If containment turns out to be impossible other defenses become more important.

Vaccines would be the ideal next line of defense but the very earliest we could expect help from a vaccine is a year from now. Since SARS is most likely a virus and anti-viral drugs are very difficult to develop the prospects on that front are not hopeful either. The best potential treatment is gamma globulin taken from the blood of people who have recovered from SARS. That may lower the fatality rate of SARS though likely only in industrialized countries and among elites in less developed countries. SARS could become pandemic in less developed countries and travel from those countries to industrialized countries could continually reintroduce it into the countries whose public health infrastructures allow them to stop its spread. Think of a series of fire alarms continually going off all across the industrialized countries as small outbreaks cause a series of small scale quarantines. That might turn out to be our future until a SARS vaccine is developed.

Another possible avenue of treatment is to find a way to suppress the most deadly symptom of SARS: the accumulation of fluids in the lungs which caused SARS to initially be called atypical pneumonia. The key to prevention of the fatal accumulation of fluids may be to find a way to suppress the production or sensing of the natural inflammation signalling compounds called cytokines. It is too early to tell whether steroids (which also suppress immune response) can suppress cytokines enough without suppressing the immune system too much.

With containment looking less likely, the availability of vaccines too distant in the future, and the development of drug regimens that prevent fatal consequences still in doubt the best response to SARS may turn out to be widespread changes in lifestyles and work habits to decrease the chances of spread. The widespread wearing of surgical masks as now seen publically in Hong Kong may spread to other areas where SARS takes hold. Health checks on airline passengers and the wearing of surgical masks on air flights might also become commonplace. The air filtration systems in many commercial and residential buildings may be quickly upgraded to prevent airborne virus spread.

Here's where the effect of SARS may become counter-intuitive: Because it kills only 3 or 4 percent of its victims a widespread public reaction that seeks to reduce the risk of exposure will have the added benefit of reducing the spread of influenza. This could lead to a net reduction in total deaths caused by infectious diseases because estimates of the yearly death toll in the United States from influenza run from 20,000 to 36,000 on average. The yearly death toll estimated as due to influenza in Canada runs from 1,500 to 4,500. Other industrialized countries have similar yearly death tolls from influenza proportionate to their populations. However, since influenza is more likely to kill the elderly the numbers also vary depending on the age distribution of the population and on the rate of yearly immunization. Also, death from influenza does not take as many total years of life away as a disease that strikes people down at a younger age. Still, if the populations of industrialized societies take drastic measures to reduce their risk of getting SARS one likely side effect should be a reduction of the death toll from influenza and possibly from other infectious diseases as well. Even those who are not at risk of dying from influenza will enjoy the benefit of being sick less often and employers will suffer lower amounts of lost work days and reduced productivity days due to sickness.

Update: A doctor in Hong Kong says Westerners fleeing Hong Kong are helping to spread the SARS virus more widely.

Dr David Stirling, told The Telegraph that families trying to escape the outbreak of the incurable illness - which has killed 80 people worldwide - were now the most likely reason for the spread of Severe Acute Respiratory Syndrome.

Update II: Time Magazine has an excellent article that compares the approaches used by Singapore and Hong Kong to respond to the outbreak of SARS. The far more aggressive measures pursued by Singapore resulted in the control of the outbreak.

When new cases were discovered, a team of 100 "contact tracers" tracked down not only patients' immediate families, friends and neighbors but also their office colleagues and favorite food hawkers, and placed them in quarantine, too. Anyone suspected of having SARS is transported to the hospital in an ambulance.

Singapore's far more aggressive approach toward identifying patient contacts and quarantining them has led to a decline in the number of new SARS cases in Singapore. It still may be possible to contain SARS if that aggressive approach is applied in other areas of SARS outbreak.

Update III: SARS may have gotten spread thru the Amoy Garden apartment complex in Hong Kong via cockroaches. If this turns out to be true then it will make SARS harder to contain.

Share |      Randall Parker, 2003 April 06 12:32 PM  Dangers Natural Bio


Comments
David Alexander MITCHELL said at April 17, 2003 12:21 PM:

I have a question. All old people and some others in Quebec have a once-in-a-lifetime injection of 'Pneumovax'. Is it possible that would make the difference between those who suffer the pneumonia aspect of SARS and those who do not? Does anyone know?

David Mitchell

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