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Suggested Citation:"BACKGROUND." National Research Council. 2008. Technical Input on Any Additional Studies to Assess Risk Associated with Operation of the National Emerging Infectious Diseases Laboratory, Boston University: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/12208.
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Suggested Citation:"BACKGROUND." National Research Council. 2008. Technical Input on Any Additional Studies to Assess Risk Associated with Operation of the National Emerging Infectious Diseases Laboratory, Boston University: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/12208.
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Suggested Citation:"BACKGROUND." National Research Council. 2008. Technical Input on Any Additional Studies to Assess Risk Associated with Operation of the National Emerging Infectious Diseases Laboratory, Boston University: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/12208.
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Suggested Citation:"BACKGROUND." National Research Council. 2008. Technical Input on Any Additional Studies to Assess Risk Associated with Operation of the National Emerging Infectious Diseases Laboratory, Boston University: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/12208.
×
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Suggested Citation:"BACKGROUND." National Research Council. 2008. Technical Input on Any Additional Studies to Assess Risk Associated with Operation of the National Emerging Infectious Diseases Laboratory, Boston University: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/12208.
×
Page 8
Suggested Citation:"BACKGROUND." National Research Council. 2008. Technical Input on Any Additional Studies to Assess Risk Associated with Operation of the National Emerging Infectious Diseases Laboratory, Boston University: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/12208.
×
Page 9
Suggested Citation:"BACKGROUND." National Research Council. 2008. Technical Input on Any Additional Studies to Assess Risk Associated with Operation of the National Emerging Infectious Diseases Laboratory, Boston University: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/12208.
×
Page 10
Suggested Citation:"BACKGROUND." National Research Council. 2008. Technical Input on Any Additional Studies to Assess Risk Associated with Operation of the National Emerging Infectious Diseases Laboratory, Boston University: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/12208.
×
Page 11
Suggested Citation:"BACKGROUND." National Research Council. 2008. Technical Input on Any Additional Studies to Assess Risk Associated with Operation of the National Emerging Infectious Diseases Laboratory, Boston University: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/12208.
×
Page 12
Suggested Citation:"BACKGROUND." National Research Council. 2008. Technical Input on Any Additional Studies to Assess Risk Associated with Operation of the National Emerging Infectious Diseases Laboratory, Boston University: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/12208.
×
Page 13
Suggested Citation:"BACKGROUND." National Research Council. 2008. Technical Input on Any Additional Studies to Assess Risk Associated with Operation of the National Emerging Infectious Diseases Laboratory, Boston University: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/12208.
×
Page 14

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BACKGROUND In 2003, the Boston University (BU) Medical Center was awarded a $128 million grant from the National Institutes of Health (NIH) to build one of two national maximum- containment laboratories for research on biological pathogens. The National Emerging Infectious Diseases Laboratory (NEIDL) is part of the National Institute of Allergy and Infectious Diseases efforts to provide physical infrastructure for the conduct of biodefense and emerging-infectious-disease research to develop new and improved approaches to treating, preventing, and diagnosing a variety of bacterial and viral diseases. Diseases to be studied include biothreat agents and emerging novel pathogens, such as those which cause Ebola, Marburg, plague, dengue fever, Lassa fever, shigellosis, and unusual virulent influenzas. The facility will include a biosafety level-4 (BSL-4) and several BSL-3 containment laboratories housed in a 223,000-ft2 building. Under the National Environmental Policy Act (NEPA), NIH reviewed the potential impacts of the NEIDL at its location 3 in Boston's South End. The review concluded that the facility would not pose a risk to the community. However, the location of the facility on Albany Street in Boston's South End, which includes environmental justice communities with large low-income and minority populations, is controversial, and there have been numerous contentious public meetings about the plans for the facility. Three legal actions have been filed to stop the funding and construction of the NEIDL. NIH prepared a document, “Draft Supplementary Risk Assessment and Site Suitability Analyses” (DSRASSA), regarding the siting and operation of the BU NEIDL in response to comments from the federal court presiding over a NEPA lawsuit. The DSRASSA was prepared to supplement NIH's previous assessments of the potential risks posed by the NEIDL at its current location in Boston. In 2007, the Massachusetts Executive Office of Energy and Environmental Affairs (MEOEEA) asked the National Research Council to establish a committee to provide technical input on the NIH DSRASSA to the MEOEEA. Although the DSRASSA was prepared in response to comments that arose in federal litigation pursuant to the NEPA process, the MEOEEA requested a review because it expected the DSRASSA to be an integral part of the material that would be submitted to it by BU in fulfillment of Massachusetts Environmental Policy Act (MEPA) requirements. The National Research Council Committee on Technical Input on the NIH's Draft Supplementary Risk Assessment and Site Suitability Analyses reviewed the DSRASSA and discussed its methods and analyses to address the specific questions posed by the MEOEEA (see below). In November 2007, the committee released its letter report answering these questions. The committee's letter report was critical of the DSRASSA, finding that it was not sound and credible, did not adequately identify and thoroughly develop worst-case scenarios, and did not contain the appropriate level of information to compare the risks associated with alternative locations. The letter report also raised specific concerns about agent selection, scenario development, modeling methodology, consideration of environmental justice issues, and risk communication. 3 Construction of the laboratory building is nearly complete. The remaining issue is whether the BSL-4 component will become operational. 4

In March 2008, NIH announced that additional steps would be taken to address judicial requests and public comments on risks associated with the siting and operation of the NEIDL (see http://nihblueribbonpanel-bumc-neidl.od.nih.gov/roster.htm for a list of blue ribbon panel members.) Specifically, NIH established a blue ribbon panel of outside experts to advise NIH on how to respond to comments by the courts and the public regarding possible risks associated with the siting and operation of the NEIDL. An early task of the panel will be to advise NIH on the development of a statement of work for any risk analyses that may be necessary later. Given prior National Research Council comments on the DSRASSA, NIH also asked the Research Council to reconvene the Committee on Technical Input on the NIH's Draft Supplementary Risk Assessment and Site Suitability Analyses to obtain additional insights on scope and methodologies for future risk analyses from the NRC Committee. INTRODUCTION AND COMMITTEE’S CHARGE The report prepared by the committee and released for publication on November 29, 2007, was a review of a document prepared by NIH (now called the DSRASSA but also called the NIH study and the DSER in the November 2007 report) for the MEOEEA. The committee was asked by Massachusetts to carry out a technical review of the scientific adequacy of the DSRASSA and to address three specific questions: • Are the scientific analyses in the DSER sound and credible? • Has the NIH identified representative worst case scenarios? • Based on comparison of risk associated with alternative locations, is there a greater risk to public health and safety from the location of the facility in one or another proposed location? These three questions were not developed by the committee but rather were negotiated as part of the statement of task agreed on between the National Research Council and Massachusetts to guide the committee’s work. In its November 2007 report, the committee addressed the three questions and concluded that the DSRASSA had significant deficiencies in scientific adequacy. The committee described the deficiencies in relation to the three questions. It did not focus attention on how the deficiencies might be remedied, whether they were limited to the single work product it reviewed, or whether they reflected problems in previous NIH work products to assess the potential impacts of the NEIDL. In the present report, the same committee is responding to a request from NIH to provide input and assistance on the scope and design of any additional studies that may be needed to assess the risks associated with the siting and operation of the NEIDL. The committee’s new statement of task is as follows: The NRC Committee on Technical Input on the NIH's Draft Supplementary Risk Assessments and Site Suitability Analyses (DSRASSA) for the Boston University (BU) National Emerging Infectious Diseases Laboratories (NEIDL) will be reconvened to provide input on the scope and design of any additional studies that may be needed to assess risk associated with the siting and operation of the NEIDL. The original NRC Committee was appointed to provide technical input on the DSRASSA as requested by the 5

Massachusetts Executive Office of Energy and Environmental Affairs. The Committee's letter report, which was released in November 2007, was critical of the NIH's draft document, with specific concerns raised about agent selection, scenario development, modeling methodology, consideration of environmental justice issues, and risk communication. The NIH has now appointed a Blue Ribbon Panel to advise NIH on responding to judicial and public concerns about the siting and operation of the BU NEIDL and to recommend any additional risk assessment studies that may be needed. Given prior NRC comments on the DSRASSA, the NIH is asking the NRC Committee for input on any further supplementary risk assessments that NIH might undertake. The reconvened NRC committee will prepare a brief letter report summarizing its views on the scope (e.g., worst case scenarios, alternative sites, BSL-3 and BSL-4 facilities, selection of agents, etc.) and methodological approaches to be taken to improve any additional risk assessment studies NIH prepares and will discuss these views with the Blue Ribbon Panel in a meeting or conference call after the letter report is delivered to the NIH. As in its first report, in addressing this charge from NIH, the committee did not review the content of previous documents (such as the original environmental impact statement or environmental impact report) or the scope of what has already been done to address risk and community concerns. The committee restricted its comments to suggestions based only on its review of the DSRASSA and on improving the risk assessments presented therein as input to any additional studies that may be needed to assess risk associated with the siting and operation of the NEIDL. The committee prepared this report largely on the basis of the analysis and discussions that went into the preparation of its November 2007 report, discussions that were expanded on in a series of conference calls held in April 2008. Additional input from outside the committee was not solicited beyond the standard National Research Council review process. As noted in its previous report, the committee acknowledges here—and wishes to emphasize—the need for biocontainment laboratories, including BSL-4 laboratories. These laboratories can conduct valuable scientific research. The committee also recognizes that BSL-4 facilities are being operated safely in both urban and rural areas. However, the committee’s view remains that the selection of sites for high-containment laboratories should be supported by detailed analyses and transparent communication of the available scientific information regarding possible risks. COMMITTEE’S SUGGESTIONS AND RECOMMENDATIONS Risk assessment can and should be used to address both the probability and the consequences of adverse events, such as the release of human or animal pathogens from a biocontainment facility that leads to morbidity and mortality. Risk assessment is generally an appropriate approach for characterizing risk and, when performed well and directed at answering the right questions, can assist in decision-making (such as siting decisions) and in addressing public concerns. It provides a framework for organizing information about a situation that may be highly complex and involve uncertainties with respect to matters on which experimental data are sparse or absent. Risk assessment does not generally produce a precise quantitative risk value, but it can be used to summarize 6

whatever information is available and provide insights to improve understanding and suggest new research that is needed. Such understanding, in turn, can be used to design appropriate mitigation and response strategies. The risk assessment process should be transparent, and it should inform the parties who have decision responsibility so that they are better able to make decisions, in this case, about measures to ensure the safe siting, design, and operation of the laboratory. The communities of professionals in risk analysis and infectious disease, working together, can provide specific guidance in these fields, and NIH should seek to use the best knowledge and talent available in the two communities in any future risk assessments. Scientifically sound documents can help NIH address the public’s concerns and provide information requested by the courts about site comparisons. Reviewing the scope and content of previous project documents is not within the committee’s scope of work, but the committee is pleased to make suggestions about approaches for the blue ribbon panel to consider. The committee cannot comment on the cost of such measures or on what resources are needed. The committee has elected to structure its suggestions for the blue ribbon panel around a small number of overarching questions (Kaplan and Garrick, 1981) about the risks associated with operating the NEIDL: • What could go wrong? That is, what might be the sequence of events that could cause an infectious agent to escape the laboratory, set up a chain of transmission, and cause infectious disease in the surrounding community? • What are the probabilities of such a sequence of events? • What would be the consequences of such a sequence of events? What Could Go Wrong? Scenarios of Release of an Infectious Agent The committee is aware that the courts asked for a description and evaluation of “worst-case scenarios” and reiterates that the question of whether NIH had provided representative worst-case scenarios in the DSRASSA was specifically posed to the committee by the MEOEEA. However, the committee does not endorse an exclusive focus on the development of worst-case scenarios as an appropriate procedure for carrying out risk assessments for the NEIDL or for other facilities of this type. Rather, the committee suggests two phases of analysis. The first phase is risk assessment based on a variety of plausible scenarios designed to allow a realistic assessment of risks associated with the NEIDL in general and to illuminate the comparative risks to the communities at the three sites evaluated in the DSRASSA. This analysis would not represent worst-case scenarios; rather, it could lay out realistic situations, such as protective features in place, public health mitigation strategies in place, and training and standard operating procedures followed. In a second phase, a highly unlikely but still credible high-consequence event could be analyzed. This might be referred to as a worst-case scenario, although the committee encourages NIH to define clearly what it means if it uses this term. This phase of the analysis could examine possible sequences of post-release events to explore the magnitude of the possible consequences of a release, 7

perhaps by considering such details as highly effective transmission (large R0 4 ) and a long latent period during which infectious symptoms are nonspecific or not evident. The effects of limitations in the public health and emergency response systems could also be analyzed. Any future risk assessments should incorporate sufficient meaningful biological data in the scenarios to make it possible to understand how the results of the analyses were reached. Although engineering and design—and hence safety—of high-containment biological laboratories have undoubtedly improved greatly with contemporary practices, accidental releases due to human error or maintenance failures certainly can still occur. Recent such events include the infection of workers with Brucella at one of Texas A&M University’s BSL-3 laboratories in 2006; a 1-hour power outage in 2007 at the new BSL- 4 facility of the Centers for Disease Control and Prevention in Atlanta, before work with pathogens began, wherein the main and backup power systems both failed and the negative-air-pressure system, a key element of pathogen containment, shut down; and, also in 2007, a release of foot-and-mouth disease to livestock on farms near the Pirbright high-containment laboratory in the United Kingdom due to a damaged and leaking drainage system at the facility (GAO 2007). Scenarios for evaluating the risks posed by the NEIDL should systematically include potential realistic means of biological-agent escape and should describe the various safeguards to protect laboratory workers and the surrounding community. The committee recommends that discussions of potential agent release include • Procedural or work-practice failures, including those which lead to worker exposures and infections. • Biocontainment-system and equipment failures. • An appropriate array of malevolent actions. Within these categories, one could consider contamination of the waste stream from the laboratory, the effects of power outages, unintentional or malevolent infection of laboratory workers, and unintentional or malevolent release of laboratory animals or pests (such as insects capable of serving as disease vectors). Designing scenarios in this way may also highlight where additional measures might prove useful for enhancing laboratory safety. The DSRASSA assumed, for purposes of providing an initial case for modeling, that a release occurred. Scientifically accurate scenarios that include probabilistic evaluation (see next section for discussion of probabilistic evaluation) of how a biological agent could be released could lead to enhanced preventive measures. For example, an assessment might highlight the importance of laboratory-worker training or of occupational health surveillance. Or it could lead to the recommendation of interventions instituted in other laboratories, such as working with vectorborne agents during seasons when the vectors are not circulating in the community. 4 Theoretically, R0, the basic reproduction number, is defined as the average number of secondary cases generated by a single primary case during its entire period of infectiousness in a completely susceptible population (Diekmann and Heesterbeek, 2000). 8

In addition to laboratory-related interventions to minimize the occurrence of such events (that is, prevention measures), risk assessments should address the capabilities of the medical and public health systems to respond to untoward events (that is, mitigating measures) at the South End and alternative sites. These measures are especially important to consider in the context of environmental justice, potentially unequal access to health care among the three sites, and other factors of importance to the communities. Without the discussion of preventive and mitigating measures, scenarios do not reflect how the laboratory is intended to be operated and managed, and risks are obscured to the detriment of decision-making. Basing scenarios on as much factual information as possible will make them more relevant and ensure that they portray more accurately the hazards associated with work in high-containment (BSL-3) and maximum-containment (BSL-4) laboratories. What Could Go Wrong? Agents to Consider for Risk Assessment The characteristics of a particular infectious agent may make it more or less likely that the agent could lend itself to the establishment of a chain of transmission that leads to the spread of infection in the community. The DSRASSA analyzed the potential for disease spread by four pathogens, but all four were of low transmissibility and not likely to spread beyond the persons initially infected. As noted by the committee in its November 2007 report, “Because the probability of transmission of disease from one person to another was set to be low, infections die out, rather than propagate. As a result, for all four of the agents considered, the risks calculated from the two models are small.” The committee believes that many of the agents mentioned as expected to be studied at the NEIDL (Klempner, 2008) are candidate agents with higher transmission rates that could be addressed in risk assessments regardless of the biosafety level at which they will be studied. Including both BSL-3 and BSL-4 agents in any future risk assessments is appropriate because the reasons for studying a biological agent under BSL-3 vs BSL-4 conditions include factors other than the risk associated with release of an agent (BMBL 2007). These factors include, for example, risk to laboratory workers and whether or not the agent is endemic. BSL-3 laboratories are used to study biological agents that are potentially lethal and that are transmissible by the aerosol route. It is thus possible that BSL-3 agents have greater transmissibility than some BSL-4 agents. BSL-4 agents may produce higher mortality and lack treatment options, but morbidity is also important in evaluating risk. In addition, engineered controls are greater in BSL-4 facilities, and it is possible that risks of human error are greater in BSL-3 laboratories. The committee recommends that for any future assessments NIH select a variety of agents with appropriately diverse transmission characteristics (bloodborne, transmitted on fomites, spread by aerosol, and/or requiring vectors and the potential for maintenance in existing reservoir species). In addition to portal of entry into the host, such aspects of transmission as high or low R0, latency, and incubation periods should be thoroughly addressed. Furthermore, NIH should describe why specific agents were ultimately selected for the analysis. The committee is aware of the degree of complexity involved in this task, but it is a cornerstone of assessing and communicating biological risk reliably and realistically. 9

The committee believes that it may be helpful for NIH to clarify for the public and the courts what agents and forms of agents will not be researched at the NEIDL for reasons that are likely to apply in the future. Examples may include the virus that causes smallpox and dry, powdered agents that are more easily spread in the air. A sound and well-documented rationale could be provided to substantiate why particular agents or forms of agents will not be studied. The rationale may include legal or treaty constraints and prohibitions, the fact that government agencies other than NIH are charged with missions involving work with particular agents and forms of agents, and circumstances surrounding the acquisition of agents. For example, NIH might clarify that no offensive biological weapons research will be conducted at the NEIDL, because it is prohibited by the biological weapons convention (Convention on the Prohibition of the Development, Production, and Stockpiling of Bacteriological (Biological) and Toxin Weapons and on Their Destruction). This treaty prohibits signatories from developing, producing, stockpiling, or otherwise retaining microbial or other biological agents or toxins, whatever their origin or method of production, of types and in quantities that have no justification for prophylactic, protective, or other peaceful purposes. What Are the Probabilities? Risk assessment addresses both the probability and the consequences of adverse events. The scenarios and agents discussed above should be used in any future risk assessments to analyze and communicate the probabilities of adverse events. The committee recommends that discussions of potential agent release include probabilistic statements regarding the three categories of release discussed above: • Procedural or work-practice failures, including those which lead to worker exposures and infections. • Biocontainment-system and equipment failures. • An appropriate array of malevolent actions. The development of these probabilistic statements should draw on information that already exists (for example, Johnson, 2003a, 2003b, 2004) and other risk assessment documents despite the fact that inherently the information is not comprehensive. NIH could also update previously generated quantitative measurements of safety records for its own and other contemporary BSL-3 and BSL-4 laboratories over the last 20 years, including consideration of recent accidents and exposures to inform the process. Such a quantitative analysis could include estimates of person-hours worked, numbers of laboratory-acquired infections, outcomes of infections in workers and the community, biological agents involved, and other measures relevant to biocontainment work. The historical experience of biocontainment facilities—both those associated with NIH activities and the many similar facilities around the world—is that releases of disease pathogens have been rare. There have been laboratory-acquired infections, but the resulting diseases have mostly been confined to the facilities’ workers and, in a few cases, members of their immediate families or health care providers (Harding and Byers, 2006). As noted above, contemporary BSL-3 and BSL- 4 facilities minimize the probability that a release will occur with extensive equipment and design features, 10

laboratory protocols for safety, and rigorous occupational health programs. In addition, specialized patient isolation facilities are generally available at local hospitals in the event that workers become ill after an inadvertent exposure. An infectious agent release could have a variety of consequences, and an assessment should account for them. These consequences can be conceptualized as a continuum that ranges from few or no adverse outcomes (requiring minimal or no public health response) to amplified disease transmission resulting in a public health emergency. To illustrate the continuum in more detail, the committee has described four possible scenarios that are points along it. The committee has provided examples for each scenario. Although the examples represent public health events that have been documented in the literature, the committee emphasizes that they are not based on releases from BSL-4 laboratories. • No subsequent transmission, following a small initial pool of infection. The agent may fail to establish a productive chain of transmission after only a few people are initially infected. An example is the 2003 monkeypox outbreak in the United States, which is thought to have been related to contact with pet rodents. • Little or no subsequent transmission, following multiple exposures. The agent may fail to establish a productive chain of transmission after multiple initial exposures. An example is the intentional contamination of food with Salmonella that infected hundreds of consumers but failed to spread in the community. • Limited transmission that is contained by public health measures. The agent may establish a successful chain of transmission but be controllable by public health measures (tens to perhaps hundreds or thousands of people infected). An example is the SARS outbreak observed in 2003 (Lipsitch et al., 2003). • Amplified transmission. The agent may establish a chain of transmission that amplifies rapidly and is not controlled by public health measures, which may be ineffective or overwhelmed (say, 10,000 people infected). Examples are the outbreaks of influenza, smallpox, and poliomyelitis before the availability of effective vaccines for these agents. A basic risk assessment should begin with these four possible outcomes and assess how the characteristics of agents that might be studied in the NEIDL influence the likelihood of each outcome in the event of a release. This basic approach should be a minimal requirement for risk assessment. A qualitative approach to this assessment might consider actual events, taking into consideration important differences, such as metropolitan settings and circumstances, and qualitative consideration of transmissibility (R0) and the proportion of transmission that occurs before onset of symptoms. R0 is a key quantity in estimating transmissibility of infectious diseases, and the proportion of 11

transmission that occurs before the onset of overt clinical symptoms can affect the success of public health measures (Fraser et al., 2004). Even a qualitative analysis of potential outcomes should consider impact of local characteristics (for example, population density, vector availability, and public health infrastructure) on the probability of the various outcomes. More complex approaches to predicting outcome, such as modeling, if pursued, should be rigorously justified and should be designed to build on this basic analysis (see next section). What Would Be the Consequences? The consequences of a release of an infectious agent from a high-containment laboratory depend on numerous factors, such as the characteristics of the agent, the pathway by which it is spread, and the size and characteristics of the population that is exposed to it. The major concern is the potential for community outbreaks of disease, taking into account both morbidity and mortality. The previous section discussed the need for an assessment of agents and the probability of different outcomes in the event of a release. This section discusses modeling, which is of course, another way of assessing how the disease caused by an agent may spread. Modeling may also be an important tool in devising appropriate mitigating strategies. Calculating the outcome of a release of a biological agent with models is extraordinarily difficult. The basic test of a model is whether it can replicate the various types of outcomes that are known to happen, but our understanding of any individual agent is incomplete, to say the least. Furthermore, the biology of agents within experimentally infected animals or infected humans is much better understood than the process of transmission, about which relatively little is known although it is a major parameter in determining the results of a release. For example, the observation that there are “superspreaders”, a small proportion of hosts that account for a large portion of the amplification of an epidemic, makes estimates of average transmission rates highly questionable. Likewise, it is difficult to estimate the number of contacts between people although recent estimates of age-specific contact rates from surveys that are relevant for respiratory spread of infectious diseases have become available for some populations (Mossong et al., 2008). The ability of a single model to simulate accurately both the transmission of an aerosol-transmissible agent and that of a fomite-transmitted agent is questionable. These uncertainties and complexities compound as the number of model parameters increases. There is no consensus on an approach to model all, or even many, infectious diseases. In the absence of an accepted approach, simplicity has advantages: the behavior of simple models is relatively well understood, and the effects of changing inputs are relatively transparent. More complexity and detail may not add to confidence or accuracy of model results, particularly if the data used to develop input are scant and there are many uncertainties. In short, although mathematical models of infectious diseases at the population level may provide results that can give us perspective and insight as to how and why infectious diseases cause epidemics, there is great complexity in using them and in interpreting their results. The use of models cannot make up for what is often a deficiency 12

of biological and other data, so it is essential that the judgment of epidemiologists, infectious disease specialists, and microbial risk assessors be applied to the interpretation of model results. If NIH decides that there is a compelling rationale for the use of mathematical modeling in any future risk assessments, the modeling must be done credibly, transparently, and to professional standards by an experienced team of epidemiological modelers and microbial risk assessors. The results should be interpreted in light of the strength of the data used to develop them. If modeling is deemed necessary to study the effects of an infectious agent release into a community, the type of model used should be considered case by case. If the objective is to evaluate epidemic characteristics—such as size, peak, and duration— dynamic compartmental epidemic models based on differential equations can be useful (Anderson and May, 1991). Most mathematical models used in the literature to date are simple compartmental models of various levels of complexity, such as those used to study the SARS epidemic (see, for example, Lipsitch et al., 2003). Dynamic models based on differential equations are tractable for systematic uncertainty and sensitivity analyses. In contrast, large-scale agent-based models are increasingly used to assess the role of specific control interventions in specific settings. However, these large-scale agent-based models are typically difficult to calibrate and require large-scale computing resources. Independently of the type of approach used, the model-building procedure and the procedure for assigning values to parameters need to be clearly laid out and justified. For example, which parameter values are supported by the literature, which are estimated from empirical data, and how estimates were derived need to be transparent and clearly presented. The level of detail in a model should be defended with appropriate empirical data and reference to appropriate scientific literature. The infectious disease transmission potential and uncertainty of transmission must be quantified to determine the disease related impact on the population of a release of an infectious agent. Any modeling exercise should be accompanied by thorough uncertainty and sensitivity analyses. As pointed out in the committee’s November 2007 report, assessing the uncertainty of parameter values and the sensitivity of model outputs to them is crucial. Uncertainty analysis includes assessment of the uncertainty in epidemic size, peak, and duration as parameter values vary within plausible ranges. It is especially important to consider the impact of values used for infectious disease transmission potential. Because each set of plausible model values is not equally likely, values can be drawn from appropriate probability distributions with simple random sampling or Latin hypercube sampling (see, for example, Blower and Dowlatabadi, 1994; Chowell et al., 2004). Similarly, sensitivity analysis should be conducted to assess the effects of changes in parameter values on specific model outputs, such as those described above. A sensitivity analysis will help to rank parameter values according to the size of their effect on model output. As discussed in the qualitative description above, modeling approaches should also consider the impact of local conditions (for example, population density, vector availability, and public health infrastructure) on the consequences. It would be useful to consider the possibility that different disease spread outcomes have different implications for the population immediately surrounding the laboratory (see the next section). 13

Including Community Characteristics The characteristics of the surrounding community—such as its racial, ethnic, and socioeconomic composition; its access to health care and health services; and the environmental stressors it faces—should be taken into account in the risk assessment and analysis. Urban communities often face environmental and other stressors that wealthier communities do not face. These factors are important because communities, such as the South Boston neighborhoods that surround the NEIDL, face challenges that could affect, among other things, the transmission of infectious disease, the health consequences, and the scope and deployment of public health resources required for response. It is also important to include these factors in an analysis because they form the basis of many community and environmental justice concerns about the siting of the NEIDL. Site selection can contribute to the probability of various possible outcomes. The potential for various outcomes to have different effects on sites is noted above on page 13. If modeling is used, these factors could be incorporated into the modeling exercise (see, for example, Halloran et al., 2008). If another approach is chosen, or if a modeling approach that does not accommodate the inclusion of environmental justice concerns is used, the risk assessment should adopt another quantitative or qualitative technique that reflects the community’s attributes. Improving Communication of Risk In its November 2007 report, the committee discussed risk communication aspects of the DSRASSA. The report noted that particularly in cases where there is strong public interest, such as this siting decision, it is important to develop presentations and documents that are transparent and complete and that clearly address the concerns of affected and other interested parties. There are many information resources on risk assessment and risk communication, and NIH should use the wisdom accumulated in the published literature on effective communication of risk. Although the committee has not described the specifics of risk communication in this report, it notes that a recent article by Race (2008) analyzes public review processes and risk communication with respect to a number of high-containment laboratories recently built or under construction. Many of the laboratories that generated serious controversies had key issues in common, including concerns about trust, transparency, and the reporting of accidents. Lofstedt (2002) and Fell and Bailey (2005) also discuss risk communication in connection with laboratory siting. Finally, the committee refers the blue ribbon panel to the risk communication concepts discussed in the National Research Council reports Improving Risk Communication (1989) and Understanding Risk: Informing Decisions in a Democratic Society (1996). 14

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