How Accurate Is Anthrax Detection?
Jim Kouri, CPP
June 20, 2005
In September and October 2001, letters laced with Bacillus anthracis (anthrax) spores were sent through the mail to two US senators and to members of the media. These letters led to the first US cases of anthrax disease related to bioterrorism. In all, 22 individuals, in four states and Washington, DC, contracted anthrax disease; 5 died. These cases prompted Congress to ask GAO to describe and assess federal agencies' activities to detect anthrax in postal facilities, assess the results of agencies' testing, and assess whether agencies' detection activities were validated.
The US Postal Service, Centers for Disease Control and Prevention, and Environmental Protection Agency conducted several tests, including sample collection and analytic methods, to detect anthrax in postal facilities in 2001. They developed a sampling strategy and collected, transported, extracted, and analyzed samples.
They primarily collected samples from specific areas, such as mail processing areas, using their judgment about where anthrax would most likely be found--that is, targeted sampling. The agencies did not use probability sampling in their initial sampling strategy. Probability sampling would have allowed agencies to determine, with some defined level of confidence, when all results are negative, whether a building is contaminated.
The results of the agencies' testing in 286 postal facilities were largely negative--no anthrax was detected. However, agencies did not use validated sample collection and analytical methods. According to the agencies, validated methods were not available in 2001. Thus, there can be little confidence in negative results.
Validation is a formal, empirical process in which an authority determines and certifies the performance characteristics of a given method. Consequently, the lack of validation of agencies' activities, coupled with limitations associated with their targeted sampling strategy, means that negative results may not be reliable. In preparing for future incidents, the agencies have made some changes based on what has been learned about some of the limitations of their sampling strategies and made some revisions to their guidelines.
In addition, the Department of Homeland Security has taken on the role of coordinating agencies' activities and has undertaken several new initiatives related to dealing with anthrax and other bio-threat agents. However, while the actions DHS and other agencies have taken are important, they do not address the issue of validating all activities related to sampling. Finally, the agencies have not made appropriate and prioritized investments to develop and validate all activities related to other bio-threat agents.
DHS stated that while it has the overall responsibility for coordination, EPA has the lead role in responding to biological attacks. However, DHS stated that it will coordinate with EPA to ensure that appropriate investments are made to explore improved sampling. But concerning our recommendation about probability-based sampling strategies, DHS said that it first wanted to develop sampling requirements and then evaluate both targeted and probability-based sampling against those requirements.
The threat of bioterrorism had been recognized for a considerable time in the United States, as well as internationally. Long before the anthrax incidents, several hoax letters indicating the presence of anthrax had been mailed to federal and state agencies, as well as to private sector organizations. In calendar year 2000, the Federal Bureau of Investigation (FBI) responded to about 250 cases potentially involving weapons of mass destruction. Of these, 200 were related to anthrax, although all turned out to be hoaxes.
Nevertheless, these events raised the possibility that facilities could become contaminated and would therefore have to be evaluated for environmental contamination. However, federal agencies have not been fully prepared to deal with environmental contamination, that is, anthrax released through the mail, including the potential for multiple dispersals in indoor environments.
Sources: US Centers for Disease Control, US Department of Homeland Security, Environmental Protection Agency, National Security Institute
The US Postal Service, Centers for Disease Control and Prevention, and Environmental Protection Agency conducted several tests, including sample collection and analytic methods, to detect anthrax in postal facilities in 2001. They developed a sampling strategy and collected, transported, extracted, and analyzed samples.
They primarily collected samples from specific areas, such as mail processing areas, using their judgment about where anthrax would most likely be found--that is, targeted sampling. The agencies did not use probability sampling in their initial sampling strategy. Probability sampling would have allowed agencies to determine, with some defined level of confidence, when all results are negative, whether a building is contaminated.
The results of the agencies' testing in 286 postal facilities were largely negative--no anthrax was detected. However, agencies did not use validated sample collection and analytical methods. According to the agencies, validated methods were not available in 2001. Thus, there can be little confidence in negative results. Validation is a formal, empirical process in which an authority determines and certifies the performance characteristics of a given method. Consequently, the lack of validation of agencies' activities, coupled with limitations associated with their targeted sampling strategy, means that negative results may not be reliable. In preparing for future incidents, the agencies have made some changes based on what has been learned about some of the limitations of their sampling strategies and made some revisions to their guidelines.
In addition, the Department of Homeland Security has taken on the role of coordinating agencies' activities and has undertaken several new initiatives related to dealing with anthrax and other bio-threat agents. However, while the actions DHS and other agencies have taken are important, they do not address the issue of validating all activities related to sampling. Finally, the agencies have not made appropriate and prioritized investments to develop and validate all activities related to other bio-threat agents.
DHS stated that while it has the overall responsibility for coordination, EPA has the lead role in responding to biological attacks. However, DHS stated that it will coordinate with EPA to ensure that appropriate investments are made to explore improved sampling. But concerning our recommendation about probability-based sampling strategies, DHS said that it first wanted to develop sampling requirements and then evaluate both targeted and probability-based sampling against those requirements.
The threat of bioterrorism had been recognized for a considerable time in the United States, as well as internationally. Long before the anthrax incidents, several hoax letters indicating the presence of anthrax had been mailed to federal and state agencies, as well as to private sector organizations. In calendar year 2000, the Federal Bureau of Investigation (FBI) responded to about 250 cases potentially involving weapons of mass destruction. Of these, 200 were related to anthrax, although all turned out to be hoaxes.
Nevertheless, these events raised the possibility that facilities could become contaminated and would therefore have to be evaluated for environmental contamination. However, federal agencies have not been fully prepared to deal with environmental contamination, that is, anthrax released through the mail, including the potential for multiple dispersals in indoor environments.
Sources: US Centers for Disease Control, US Department of Homeland Security, Environmental Protection Agency, National Security Institute
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