On September 24, 2005 six biodefense sensors - part of the nation's BioWatch system - detected the presence of tularemia while about a hundred thousand peoplewere on the Mall for anti war protests.
Tularemia causes flu-like symptoms and can be treated by antibiotics, but it can be fatal if left untreated. It is one of the major biohazards the Department of Homeland Security watches for, along with plague, anthrax and smallpox.
Since this detection, however, there have been no public reports of illness, and some question as to the validity of these readings.
The BioWatch system is deployed in dozens of cities nationwide, with many details remaining classified. A previous alert in Hoston in 2003 turned out to be a false alarm caused by naturally occuring bacteria.
The system is not designed to sound an immediate alarm, since analysis of sensor readings takes 36 hours. So the system is mostly useful for alerting officials to be on the watch for reports of illness. In other words, you could be exposed to a deadly substance and not told for two, three or more days.
In the recent Washington incident, the Department for Homeland Security took three days to inform the Center for Disease Control about the sensor readings. Local officials were not informed for five days, supposedly because subsequent tests called into doubt the original readings. But still, you can see that the tendency is on the side of not alerting the public.
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