Currently, the BioWatch program collaborates with more than 30 BioWatch jurisdictions throughout the nation to operate approximately 600 Gen-2 aerosol collectors. These units rely on a vacuum-based collection system that draws air through a filter. These filters are manually collected and transported to state and local public health laboratories for analysis using a process called polymerase chain reaction (PCR). Sometimes also called molecular photocopying, PCR is a technique used to amplify (or copy) segments of deoxyribonucleic acid (DNA), the building blocks of genetic material. By targeting specific segments of genetic material, PCR can be used as the basis for a test, or assay, for the presence of genetic signatures associated with specific biological organisms, such as the five BioWatch threat agents. (The program monitors for six distinct biothreat agents, but two of these are closely related, although they cause different diseases, and the BioWatch program has treated them as a single agent. For consistency, we will treat them as a single agent and report that there are five BioWatch threat agents in total.) In the BioWatch Gen-2 system, multiple PCR assays are used for each threat agent. In an initial “screening” step, one assay is run for each threat agent. If any of these assays yields a positive result, suggesting the presence of one of the threat agents, then the analysis proceeds to a “verification” step in which multiple additional assays are run targeting different genetic signatures for that agent. If the verification step also yields a positive result, then a BioWatch Actionable Result (BAR) is declared. Using this manual process, the determination of a BAR can occur from 12 to 36 hours after an agent is initially captured by the aerosol collection unit. This 36-hour timeline consists of up to 24 hours for air sampling, up to 4 hours for retrieving the sample from an aerosol collection unit and transporting it to the laboratory, and up to 8 hours for laboratory testing. Each BioWatch jurisdiction has either a BioWatch Advisory Committee or equivalent decision-making group in place, composed of public health officials, first responders, and other relevant stakeholders. The BioWatch Advisory Committee is responsible for the day-to-day BioWatch operations, including routine filter collection and laboratory analysis of filter samples. In the event of a BAR, the BioWatch Advisory Committee, in partnership with OHA and other stakeholders, is also responsible for determining whether that BAR poses a public health risk and deciding how to respond. The declaration of a BAR does not necessarily signal that a biological attack has occurred. BARs have been triggered by biological agents that occur naturally in numerous areas of the United States. From 2003 through 2014, 149 BARs were declared, but none was linked to an attack or to a public health threat. For a more detailed discussion of this issue, see appendix II. Figure 1 shows the process that local BioWatch jurisdictions are to follow when deciding how to respond to a BAR. In cooperation with other federal agencies, DHS created the BioWatch program in 2003. The goal of BioWatch is to provide early warning, detection, or recognition of a biological attack. When DHS was established in 2002, a perceived urgency to deploy useful—even if immature—technologies in the face of potentially catastrophic consequences catalyzed the rapid deployment of many technologies. In the initial deployment of BioWatch—known as Generation-1—DHS deployed aerosol collectors to 20 major metropolitan areas, known as BioWatch jurisdictions, to monitor primarily outdoor spaces. DHS completed the initial deployment quickly—within 80 days of the President’s announcement of the BioWatch program in his 2003 State of the Union Address. To accomplish this rapid deployment, DHS adapted an existing technology that was already used for other air monitoring missions. In 2005, DHS expanded BioWatch to an additional 10 jurisdictions, for a total of more than 30. The expanded deployment— referred to as Gen-2—also included the addition of indoor monitoring capabilities in three high-threat jurisdictions and provided additional capacity for events of national significance, such as major sporting events and political conventions. The technology used in Gen-1 and Gen-2 was deployed rapidly and, according to the National Academies in 2011, without sufficient testing, validation, and evaluation of its technical capabilities. To reduce the time required to detect biothreat agents, DHS began to develop autonomous detection capability in 2003 for the BioWatch program—known as Gen-3. Envisioned as a laboratory-in-a-box, the autonomous detection system would automatically collect air samples, conduct analysis to detect the presence of biothreat agents every 4 to 6 hours, and communicate the results to public health officials via an electronic network without manual intervention. By automating the analysis, DHS anticipated that detection time could be reduced to 6 hours or less, making the technology more appropriate for monitoring indoor high-occupancy facilities such as transportation nodes and enabling a more rapid response to an attack. DHS also anticipated a reduction in operational costs by eliminating the program’s daily manual sample retrieval and laboratory analysis. In 2008, DHS OHA initiated a competitive bid process for the first testing phase of the Gen-3 acquisition, known as Gen-3 Phase I. Five vendors responded to the request for proposal, and DHS awarded contracts to two, for technologies known as the Bioagent Autonomous Network Detector (BAND, later named M-BAND) and the Next Gen Automated Detection System (NG- ADS). From May 2010 through June 2011, the BioWatch program conducted Phase I testing on these candidate Gen-3 technologies. The testing goals included characterizing the state of available autonomous detection technology on the market and evaluating the candidate systems’ abilities to meet performance requirements developed by the BioWatch program. The Phase I testing consisted of testing of individual system components, such as the aerosol sampling component (the component that collects particles from the air) and the analytical subsystem (the component that detects and identifies biothreat agents), whole system chamber testing, and an operational field test in a BioWatch jurisdiction. Characterization testing did not demonstrate the system’s end-to-end ability to detect the five BioWatch threat agents in an operational environment because these agents cannot be released into the air in such environments. Expressing concern in 2011 about the rigor of DHS’s effort to help guide its Gen-3 decision making, Members of the Congress asked us to examine issues related to the Gen-3 acquisition. We released a report that evaluated the acquisition decision-making process for Gen-3 in September 2012. We recommended that before continuing the Gen-3 acquisition, DHS should carry out key acquisition steps, including reevaluating the mission need and systematically analyzing alternatives based on cost-benefit and risk information. DHS subsequently commissioned an analysis of alternatives, which was interpreted by DHS as showing that any advantages of an autonomous system over the current manual system were insufficient to justify the cost of a full technology switch. DHS’s April 24, 2014, ADM announced the cancellation of the Gen-3 acquisition and made Gen-2 the official program of record for aerosol biological threat detection. The ADM also directed S&T to explore development and maturation of an effective and affordable automated aerosol biodetection capability, or other operational enhancements, that meets the operational requirements of the BioWatch system. The capabilities of the BioWatch system can be assessed at three different levels (fig. 2). At the highest level, BioWatch consists of an array of aerosol collectors deployed in an operational environment and the associated laboratory processes for analyzing samples. The operational environment might be outdoors, as in a metropolitan area (shown in the fig. ); indoors, as in an airport; or a subway or other transit system. At this level, the capability of the system to detect an attack depends on factors that include the performance characteristics of the technology (including the aerosol collector and the technology used for laboratory analysis of samples), the number and locations of the collectors, the location of an attack (that is, where a biothreat agent is released into the air), and wind patterns (for an outdoor attack). At the next level is the detector, which consists of the aerosol collector unit and the process by which samples collected by this unit are transferred to a laboratory and analyzed. Performance and effectiveness at this level depend on the technical performance characteristics of the aerosol collector itself, the extent to which the sample is preserved intact during the collection cycle and during transport to the laboratory, and the laboratory processes that are used to prepare and analyze the sample. Finally, performance can also be assessed at the level of individual components of the detector. These include (1) the aerosol collection unit, which collects and retains aerosol particles on a filter; (2) the sample recovery process, by which samples are removed from the aerosol collector and transported to a laboratory; (3) the filter extraction process, in which aerosol particles are removed from the filter and put into a liquid solution; (4) the DNA extraction process, in which DNA is extracted from the aerosol particles in liquid solution in preparation for further analysis; and (5) the PCR assays, which are used to test for the presence of specific genetic signatures of biothreat agents (as described earlier). At the highest level—an array of detectors deployed in an operational environment—measures of performance include the system’s probability of detection (Pd) for attacks of different types and sizes. The BioWatch program employs a variation on the Pd measure that is designed to assess the system’s ability to detect attacks that could cause large numbers of casualties. Because BioWatch threat agents cannot be released into the air in operational environments, the performance of an array of detectors cannot be tested directly. One method of testing that can be used to address this limitation is the use of simulants for biothreat agents. A simulant is a selected nonpathogenic organism that mimics all or some of the physical or biological characteristics of one or more pathogenic agents. Another method that has been used for BioWatch involves computer modeling and simulation of attack scenarios.