National Museum of Health / AP Influenza victims crowd into an emergency hospital at Camp Funston, Kansas, 1918.

On the medical front, the U.S. has never been particularly good at prevention. The tack, usually, is to patch people up as they get sick, rather than keeping them from falling ill to start. But no Band-Aid is sufficient to handle a lethal pandemic, which some experts say is inevitable  if not imminent. Whether it's bird flu or some other deadly knock-out germ that eventually sweeps through the country, scientists and public-health researchers are trying to prepare for it now to ensure that everyone has a better chance of survival.

To plan for the future, researchers in Michigan went straight to the past. Led by Dr. Howard Markel, director of the University of Michigan Medical School's Center for the History of Medicine, a team of public-health experts evaluated the U.S. response to the world's last great pandemic  the Spanish flu in 1918. The new report, published in the Aug. 8 issue of the Journal of the American Medical Association, analyzed the public-health measures taken by 43 U.S. cities, all with populations greater than 100,000, during the six months between Sept. 1918 and Feb. 1919. Markel found that cities that early on adopted "old-fashioned," non-pharmaceutical interventions  such as school closures, social-distancing in the community and workplace and quarantine  and "layered" multiple interventions at once for a long period of time fared better than other cities, with slower rates of infection and lower rates of death.

"The conventional wisdom had been that cities [in 1918] had done everything they could and nothing worked  it was all doom and gloom and dread and nothing to do but throw up our hands in despair," says Dr. Martin Cetron, director of the Division of Global Migration and Quarantine at the Centers for Disease Control and Prevention (CDC), and a senior author of the study. "This study gives us real reason for optimism, that even reaching back to a time where there were no antiviral medications and no well-matched vaccines to fight a pandemic, the things communities did in terms of traditional public health tools  isolation, quarantine, social-distancing, canceling schools  made a big difference and have a lot of potential to mitigate the severity of a lethal disease pandemic."

That's good news, considering that the U.S. has purchased only 26 million doses of the newly licensed H5N1 flu vaccines, enough to cover 13 million people in the event of a pandemic but there's no guarantee that H5N1 will even be the bug in question. In 1918 the Spanish flu infected 20% of the world's population and killed 40 million people (a mortality rate of 2.5%), and 550,000 of those deaths were in the U.S. What the new study illuminates is the small print behind that big number: some cities got hit much harder than others, and there's a lot to be learned from the way they each responded to the same threat.

Markel and colleagues divided the cities' interventions into three major categories: school closure, cancellation of public gatherings, and isolation and quarantine. During the 24 weeks researchers studied, there were 115,340 excess deaths due to pneumonia and influenza in 43 states, with a collective population of about 23 million. New York City responded to its earliest sign of infection with isolation and quarantine over a sustained period of time, beginning 13 days after the first case was detected, and had the lowest pandemic-related death rate of any city on the East coast. By contrast, Pittsburgh reacted late, waiting one month, and suffered the greatest number of excess deaths from the disease. In both cities, however, interventions were used singly rather than as a combined approach. St. Louis layered its interventions, using the various social-distancing measures at once, 2.5 weeks after its first case of infection; that tactic mitigated the outbreak and St. Louis fared better than 36 other communities as a result. Researchers compare layering interventions to layering Swiss cheese: if the holes are vulnerabilities, with enough layering you'll end up with a solid block of prevention.

Though Markel's study has just been published, it has already been rolled into policy. The Department of Health and Human Services and CDC finished their analysis of the study's data last December before incorporating it into the Community Strategy for Pandemic Influenza Mitigation, a collection of guidelines for use by individuals and communities issued by the agencies in February. The guide offers help in coordinating and implementing a strategy to protect communities from the front end of an epidemic and to keep them afloat until the appropriate pandemic-strain vaccine can be delivered to them  which officials estimate will be four to six months after the first case is identified.

The context of the 21st century, however, is very different from that of 1918. Individual rights are guarded a lot more fiercely today than in the past, and people may not submit easily to compulsory quarantine or isolation. It is critical that if we were to implement such public health measures that we have adequate medical and psychological support, says Markel. "If you come down with the force of the law very hard, you have to ask if the public health edict helps public health or endangers it," he says. "The onus is on us as physicians, public health experts, government public health officers at the city, state and federal levels to embark on a huge educational campaign."

These days, too, travel  and spread of disease  is faster, but so is communication. The medical community can share information more quickly. Accordingly, there's more pressure for better and faster detection of infection. "Early needs to be earlier because things move much more rapidly," says Cetron. "It means not waiting until that death curve doubles. We want the trigger to be the first outbreak or cluster of cases of the pandemic strain in a community or state."

He adds: "We're probably the first generation in history to have the benefit of hindsight and time to plan for the future, not only to implement the measures effectively but to plan for the adverse unintended consequences of social-distancing strategies," says Cetron. Now that sounds a lot like prevention.