In the absence of detectors of an attack itself, the next line of defense would be a surveillance system that would alert health officials to clusters of people coming down with unusual symptoms.
At present, the Centers for Disease Control and Prevention in Atlanta looks at patterns of disease in reports that percolate up from doctors to local and state public health officials.
A perhaps fanciful idea would be to deploy sentinel animals, much like the coal mine canaries that died quickly if noxious gases started seeping in. Some people have recommended stationing guinea pigs or mice in strategic locations, because the animals can become sick if they inhale even a few anthrax spores.
A futuristic idea is to use living tissues, sometimes connected to electronic chips, as sensors. Scientists at MIT. Lincoln Laboratory are developing a system known as Canary in which human immune cells are genetically engineered to latch onto pathogens and emit a signal when they do.
Systems for private homes are a long way off. Wheeler said the Energy Department hoped to get the systems down to a few thousand dollars. But, he said, "It's not going to be US$29.95 at Wal-Mart."
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