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April 25, 2003

 Six Months to Act

By Donald S. Burke

SARSThe most chilling moment of my medical career occurred in 1985, when I led a program to test incoming U.S. Army recruits for HIV, the virus that causes AIDS. At the time, little was known about the emerging HIV virus or AIDS. As I began to analyze blood samples from the first 600,000 recruits, I discovered that HIV had silently infected a large cross section of apparently healthy young adults. At that moment I realized that we were already losing the race to control the virus, and that the human species was destined to be afflicted with HIV as a fact of life—and death—for decades to come.

Now the spread of SARS (the severe acute respiratory syndrome) threatens to cause another global pandemic. But this time the chances of successfully controlling the emerging microbial threat are far better and there is a real possibility we can eradicate the virus before it overwhelms global control efforts.

There are three reasons for this. Firstly, most of those infected with SARS rapidly become ill and so can be easily identified. Compared with HIV/AIDS, there seems to be much less danger of them carrying the virus for prolonged periods without any outward sign of infection, so facilitating its transmission to others. Secondly, the global medical and scientific response to SARS, led by the World Health Organization, has been prompt and forceful. Cases, and those they have been in contact with, are being tracked worldwide and—when necessary—isolated. And scientists have already identified the coronavirus that causes SARS and deciphered its genetic code. This makes it possible to test patients for the virus, and even allows doctors to measure the quantity of virus and determine which patients are most contagious.

There is also a third factor working to our advantage, and that is the simple change of seasons. Viruses that are transmitted from human to human by coughing or sneezing, like influenza, measles, and even smallpox, are strongly seasonal in nature. In winter, the epidemic is like a chain reaction; in summer, it fizzles out. Quite why this is so has never been conclusively determined. Temperature alone is not the explanation, although experimental evidence suggests that seasonal changes in humidity levels play an important role. Crowded indoor conditions, leading to more people breathing the same air, may be another factor.

Whatever the explanation, all available evidence suggests that SARS shares the same seasonal pattern. That's also true of other coronaviruses, such as those that cause epidemics among animals and benign coronaviruses in humans. And it helps explain why the present epidemic spread so rapidly in February and March and why the infection rate has now slowed (although, of course, the absolute number of cases continues to increase).

Nature has also favored us in another way. There have been relatively few cases of influenza in most countries this year, which means there is little danger of SARS patients being misdiagnosed as having flu. When patients caught fevers and showed respiratory symptoms or pulmonary problems, especially after contact with a SARS case, it was easy to be reasonably certain they had caught the coronavirus and impose strict quarantine measures before they could spread it any further.

Next winter, we may not be so lucky. If influenza and SARS epidemics strike simultaneously, confusion will reign.

As summer approaches and the SARS epidemic declines, there will be an understandable urge to celebrate. But we must eschew premature celebrations and self-congratulations. History teaches us that the devastating 1918 influenza epidemic began with a modest "herald wave" in spring that faded away during the summer, only to explode and wreak global devastation the following fall and winter. It is possible that SARS, now seeded around the globe, could follow a similar pattern and fade away this summer, only to erupt again next winter.

The coming summer lull in SARS affords an extraordinary opportunity. If we can detect, diagnose, and effectively isolate every contagious case during the period when the infection rate is at its lowest, it is possible that we can truly eradicate SARS, not just for the short term, but permanently.

Epidemic-control efforts should not simply be maintained, but doubled, and redoubled again. New diagnostic tests should be mass produced and made freely available around the globe. Epidemiological teams should investigate every possible case, even in the poorest communities. Face-saving politicians who hide local epidemics must be cajoled, or more forcefully convinced, to cooperate. Special efforts must be made to detect and quench new outbreaks in the Southern Hemisphere. With skill, determination, and luck, we might be able to break all the chains of transmission before the onset of winter offers the virus a chance to spread more rapidly again.

Technological optimists may argue that eradication is not essential, because antiviral drugs and vaccines will be developed that can control SARS. However, experience with AIDS, West Nile, and Ebola, suggests these techno-fixes will not be ready for several years, at best. On the other hand, epidemiological pessimists will warn that eradication of SARS is simply impossible. Their more nuanced counterparts will argue that, even if SARS is eradicated, it may emerge again, either naturally or through accidental biobungling. But a virus that jumps across species to cause an outbreak is a highly random event, unlikely to recur often.

Of course, the pessimists may eventually be proved correct: a halfhearted effort at controlling the epidemic would guarantee failure. But if the U.S. is prepared to lead a world-wide coalition of nations in joining forces with the World Health Organization with the goal of doing everything possible to eradicate SARS, this extraordinary goal might just be achievable.

Louis Pasteur, father of microbiology, wisely counseled that "Chance favors the prepared mind." For the moment, chance is on our side. But we have just six months to complete the job of the global eradication of the SARS coronavirus. After that, when the seasonal epidemic flares next year, it will be too late.

Dr. Burke is professor of international health and epidemiology at the Johns Hopkins Bloomberg School of Public Health in Baltimore, Maryland.

"Reprinted with permission of The Wall Street Journal Copyright 2003 Dow Jones & Company, Inc. All rights reserved."

Public Affairs media contacts for the Johns Hopkins Bloomberg School of Public Health: Tim Parsons or Kenna Brigham at 410-955-6878 or paffairs@jhsph.edu.

Photographs of Donald Burke are available upon request.