Quantitative Microbial Risk Assessment

Description

• Provides the latest QMRA methodologies to determine infection risk cause by either accidental microbial infections or deliberate infections caused by terrorism
• Reviews the latest methodologies to quantify at every step of the microbial exposure pathways, from the first release of a pathogen to the actual human infection
• Provides techniques on how to gather information, on how each microorganism moves through the environment, how to determine their survival rates on various media, and how people are exposed to the microorganism
• Explains how QMRA can be used as a tool to measure the impact of interventions and identify the best policies and practices to protect public health and safety
• Includes new information on genetic methods
• Techniques use to develop risk models for drinking water, groundwater, recreational water, food and pathogens in the indoor environment

Table of contents

PREFACE

CHAPTER 1 MOTIVATION 1

• Prevalence of Infectious Disease 1
• Prior Approaches 4
• Scope of Coverage 4
• Potential Objectives of a QMRA 5
• Site-Specific Assessment 5
• Ensemble of Sites 6
• Secondary Transmission 7
• Outbreaks versus Endemic Cases 7
• References 10

CHAPTER 2 MICROBIAL AGENTS AND TRANSMISSION 15

• Microbial Taxonomy 15
• Eukaryotes 15
• Prokaryotes 18
• Viruses 20
• Prions 22
• Clinical Characterization 24
• Microorganisms of Interest 27
• Viruses 27
• Bacteria 37
• Protozoa 42
• Transmission Routes 45
• Inhalation 48
• Dermal Exposure 50
• Oral Ingestion 50
• References 55

CHAPTER 3 RISK ASSESSMENT PARADIGMS 63

• Chemical Risk Assessment: National Academy of Sciences Paradigm 63
• Ecological Risk Assessment 67
• Approaches for Assessing Microbial Risks 71
• Background 71
• The QMRA Framework 74
• Hazard Identification 74
• Dose–Response Assessment 74
• Exposure Assessment 76
• Risk Characterization 77
• Risk Management 79
• Development of the QMRA Framework and Processes 79
• QMRA and the Safety of Water 82
• QMRA, Food Safety, and the HACCP System 84
• References 86

CHAPTER 4 CONDUCTING THE HAZARD IDENTIFICATION (HAZ ID) 91

• Identifying and Diagnosing Infectious Disease 92
• Health Outcomes Associated with Microbial Infections 95
• Sensitive Populations 100
• Women during Pregnancy, Neonates, and Young Babies 101
• Diabetes 102
• The Elderly 102
• The Immunocompromised 104
• Databases for Statistical Assessment of Disease 106
• ICD Codes 107
• Waterborne and Foodborne Outbreaks 111
• Epidemiological Methods for Undertaking HAZ ID 117
• Controlled Epidemiological Investigations 118
• HAZ ID Data Used in the Risk Assessment Process 119
• Recommendations for Updating Quantitative Data for HAZ ID Information 121
• References 122

CHAPTER 5 ANALYTICAL METHODS AND THE QMRA FRAMEWORK: DEVELOPING OCCURRENCE AND EXPOSURE DATABASES 129

• Introduction 129
• Approaches for Developing Occurrence and Exposure Databases 132
• Overview of Methodological Issues 134
• Sampling Water 136
• Sampling Surfaces and Food 138
• Sampling Aerosols 138
• Specific Techniques for Bacteria, Protozoa, and Viruses 140
• Bacteria 140
• Protozoa 142
• Viruses 143
• Molecular Techniques 145
• Probes (FISH) 146
• Typing 146
• Metagenomics 147
• PCR and Quantitative PCR 147
• References 151

CHAPTER 6 EXPOSURE ASSESSMENT 159

• Conducting the Exposure Assessment 159
• Characterizing Concentration/Duration Distributions 160
• Random (Poisson) Distributions of Organisms 160
• Estimation of Poisson Mean in Count Assay (Constant and Variable Volumes) 162
• Count Assay with Upper Limits 163
• Estimation with Quantal Assay 164
• Goodness of Fit to Poisson: Plate Assay 168
• Goodness of Fit: MPN 178
• Confidence Limits: Likelihood 182
• Implications for Risk Assessment 187
• Consumption Distributions 214
• Systematic Subpopulation Differences 221
• Afterword 223
• Appendix 224
• Microsoft Excel 224
• MATLAB 225
• R 227
• References 230

CHAPTER 7 PREDICTIVE MICROBIOLOGY 235

• Objective 235
• Basic First-Order Processes and Deviations 236
• Biological and Physical Bases for Deviations 236
• Physical Removal 238
• Types of Decay Processes 238
• General Forms of Decay and Reasons for Nonlinearity 238
• Spontaneous/Endogenous 240
• Chemical Agents 241
• Thermally Induced 243
• Ionizing and Nonionizing Radiation 243
• Predation and Antagonism 245
• Types of Growth Processes 245
• Mathematical Modeling of Growth Curves 246
• Substrate Dependency 252
• Structured Growth Models 255
• Incorporation of Decay into Growth Models 256
• Systems Biology Approaches 258
• Dependence of Growth Parameters on Other Environmental Variables 258
• Interacting Populations 258
• Data Sources 260
• References 263

CHAPTER 8 CONDUCTING THE DOSE–RESPONSE ASSESSMENT 267

• Plausible Dose–Response Models 268
• Framework for Mechanistic Dose–Response Relationships 269
• Exponential Dose–Response Model 271
• Beta-Poisson Dose–Response Model 272
• Simple Threshold Models 274
• Negative Binomial Dose Distributions 277
• Variable Threshold Models 278
• Other Mixture Models 279
• Biological Arguments for One-Hit Models 281
• Empirical Models 282
• Fitting Available Data 283
• Types of Data Sets 284
• Potential Impacts of Immune Status 298
• Relationship between Dose and Severity (Morbidity and Mortality) 299
• Morbidity Ratio (PD:I) 299
• Mortality Ratio 303
• Reality Checking: Validation 304
• Validation: 1993 Milwaukee Outbreak 304
• Use of Indicators and Other Proxy Measures in Dose–Response 305
• Indicator Methods 305
• Molecular Methods 307
• Advanced Topics in Dose–Response Modeling 308
• Dose–Response–Time Models 308
• Physiological Models 313
• Appendix 315
• References 317

CHAPTER 9 UNCERTAINTY 323

• Point Estimates of Risk 324
• Terminology: Types of Uncertainty 326
• Sources of Uncertainty 327
• Sources of Variability 328
• Variability that is Uncertain 329
• Approaches to Quantify Parametric Uncertainty 329
• Likelihood 329
• Bootstrap 330
• Other Methods 330
• Applications 332
• Exposure Assessment 332
• Dose–Response Assessment 338
• Combining Parametric Uncertainty from Multiple Sources 344
• Propagation Methods 344
• Monte Carlo Analyses 347
• Overall Risk Characterization Example 365
• Second-Order Methods 368
• Model Uncertainty and Averaging 370
• References 373

CHAPTER 10 POPULATION DISEASE TRANSMISSION 377

• Introduction: Models for Population and Community Illnesses 377
• Basic SIR Model 378
• Incubation Period 386
• Duration of Illness 388
• Secondary Cases 389
• Impact of Immunity 392
• Outbreak Detection 393
• References 397

CHAPTER 11 RISK CHARACTERIZATION AND DECISION MAKING 399

• Introduction 399
• Valuing Residual Outcomes 400
• Classical Economics 400
• DALYs and QALYs 404
• Decision Making 407
• Cost–Benefit Analysis 408
• Multivariate Approaches 411
• Other Aspects Entering into a Decision 412
• Equity and Justice Aspects 412
• References 413

INDEX 415