Race against SARS: Can pandemic be prevented?

If it spreads like flu, impact could be severe

Gerberding J. Faster . . . but fast enough? Responding to the epidemic of severe acute respiratory syndrome. Editorial. New Engl J Med — Published on-line April 2, 2003 at www.nejm.org.

The public health response to SARS has been strikingly rapid on many fronts, but a global pandemic of a new infectious disease still is a real possibility, the author warns.

"Concern is mounting about the potential for spread in schools, the workplace, airplanes, and other crowded areas," writes Julie Gerberding, MD, MPH, director of the Centers for Disease Control and Prevention.

"New cases among travelers from affected areas continue to emerge and have led to infections in household contacts and health care personnel in many countries, including the United States and Canada. The epidemic of SARS is apparently only months old, and it is entirely too soon to predict its ultimate scope or magnitude," she adds.

Epidemiologic evidence indicates that the transmission of SARS is facilitated by face-to-face contact, and this still appears to be the most common mode of spread. However, airborne transmission may have a role in some settings and could account for the extensive spread within buildings and other confined areas that has been observed in some places in Asia, she writes.

"Certainly, airborne transmission will make containment of the epidemic much more challenging," Gerberding notes.

If the new coronavirus proves to be the cause of SARS, fomite or other modes of transmission could also be relevant, since coronaviruses can survive on contaminated objects in the environment for at least a few hours and have been isolated from the stool of some animals. "Despite our long experience with other viral respiratory infections, we have no proven, successful population-based strategy for their prevention," she concedes. "Even when we have an effective vaccine, as in the case of influenza, annual infection rates and attributable mortality remain very high. If SARS transmission evolves to mimic that of influenza, containment may well be impossible without vaccination, prophylaxis, or treatment."

But there are reasons to be optimistic about future control measures, Gerberding emphasizes. Vaccines are successful in preventing coronavirus infection in animals, and the development of an effective vaccine against this new coronavirus is a realistic possibility. Likewise, novel antiviral agents, antiviral drugs in development, or existing licensed drugs could be found to provide effective prophylaxis or treatment. But can the products be made available fast enough to prevent an extensive global outbreak? Recent experience with the advances in measures against bioterrorism suggests that the pace of development can be dramatically accelerated.

"The emergence of SARS presents formidable global challenges," the author concludes. "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 in this early stage. If the virus moves faster than our scientific, communications, and control capacities, we could be in for a long, difficult race. In either case, the race is on. The stakes are high, and the outcome cannot be predicted."