WASHINGTON -- For two years, the nationwide BioWatch system, intended to protect Americans against a biological attack, operated with defective components that left it unable to detect lethal germs, according to scientists with direct knowledge of the matter.
The problem was confirmed when the Department of Homeland Security asked Pacific Northwest National Laboratory in Richland and the federal Centers for Disease Control and Prevention in Atlanta to conduct blind tests, scientists familiar with the matter said.
The federal official who oversaw installation of the components was quietly shifted to a position with no responsibility for BioWatch, and the entire episode was kept out of public view.
The U.S. Department of Homeland Security, which oversees BioWatch, opened an internal investigation, whose status remains confidential.
In more than 30 cities, BioWatch samplers located atop buildings, in train stations and in other public places suck air through dry filters around the clock. Once a day, the filters are taken to public health laboratories to be analyzed for traces of smallpox, anthrax, plague and other pathogens.
Lab technicians extract genetic material from the filters and then use kits, called assays, to release fluorescent dyes into it. When a laser is shined through the mixture, the dyes are supposed to light up if one of the pathogens targeted by BioWatch is present.
The labs originally used a series of separate assays, each designed to detect a specific germ. In 2007, Homeland Security equipped most of the labs with new kits intended to screen for multiple pathogens at the same time.
The aim was to reduce personnel costs and enable faster detection of a biological attack, and thus a speedier response.
But the new components, called "multiplex" assays, triggered false alarms, a recurring problem with BioWatch since the system was put into operation nationwide in 2003.
Homeland Security found that the kits were unsuitable for BioWatch, scientists familiar with the matter said. They spoke on condition of anonymity, citing the sensitivity of the information.
The multiplex assays could not distinguish between the bacterium that causes tularemia, a potentially deadly condition also known as rabbit fever, and similar but benign organisms called "near neighbors" that are abundant in outdoor environments.
The original assays had exhibited the same problem. But the multiplex assays had an additional shortcoming, scientists said: They were found to be far less sensitive to the presence of actual pathogens than Homeland Security officials had presumed.
In late 2009, Homeland Security officials removed the new assays and returned to using kits that searched for pathogens one at a time.