As always for a presidential inaugural, security and surveillance were extremely tight in Washington, DC, last January. But as George W. Bush prepared to take the oath of office, security planners installed an extra layer of protection: a prototype software system to detect a biological attack. The U.S. Department of Defense, together with regional health and emergency-planning agencies, distributed a special patient-query sheet to military clinics, civilian hospitals and even aid stations along the parade route and at the inaugural balls. Software quickly analyzed complaints of seven key symptoms-from rashes to sore throats-for patterns that might indicate the early stages of a bio-attack. There was a brief scare: the system noticed a surge in flulike symptoms at military clinics. Thankfully, tests confirmed it was just that-the flu.

While the January monitoring revealed nothing unusual, the deployment was just one more indicator that, long before the September 11 attacks and subsequent letter-borne anthrax assaults, U.S. security experts were taking seriously the threat of a large-scale biological attack. And for good reason. Not only could bio-agents covertly released by terrorists potentially kill hundreds of thousands, but they are extremely difficult-with currently available technology-to detect in the environment. A successful attack with biological agents-anthrax, smallpox and bubonic plague top the most-feared list-might only become clear days later, when people became seriously ill and were beyond the help of available treatments. And unlike anthrax, many bio-agents are contagious, so in any time lapse before health officials recognized an attack, victims could multiply its effect by spreading disease to others.

Already, terrorists have shown they can obtain and deliver anthrax on a small scale, and experts believe a determined group could conceivably accomplish a much larger-scale bio-attack-though it wouldn't be easy. "The level of sophistication that went into the World Trade Center attack, if applied to a chemical or biological attack, could produce an effective effort," says George Whitesides, a Harvard University chemist researching treatments for anthrax. "It is technically feasible. Whether it is politically or operationally feasible, and at what scale, we don't know. Nonetheless, we will have to prepare for the possibility, because we need an insurance policy."

That insurance policy will likely include a broad array of new technologies on at least three fronts: improved portable devices to detect and identify biological agents; new data-mining efforts to seek subtle bio-attack indicators like a spike in certain patient symptoms at emergency rooms; and improved therapies for victims. A number of these technologies have been under development for years, but in the aftermath of September 11, they're getting a renewed burst of attention from government, academic and industrial researchers.