Sattenspielfinal-feb27 February 27, 2009 The Geographic Spread of Infectious Diseases Sattenspielfinal-feb27 February 27, 2009 PRINCETONSERIESINTHEORETICALANDCOMPUTATIONAL BIOLOGY Series Editor, Simon A. Levin The Geographic Spread of Infectious Diseases: Models and Applica- tions, by Lisa Sattenspiel with contributions from Alun Lloyd Theories of Population Variation in Genes and Genomes, by Freddy Bugge Christiansen AnalysisofEvolutionaryProcesses,byFabioDercoleandSergioRinaldi Mathematics in Population Biology, by Horst R. Thieme Individual-based Modeling and Ecology, by Volker Grimm and Steven F. Railsback Sattenspielfinal-feb27 February 27, 2009 The Geographic Spread of Infectious Diseases Models and Applications Lisa Sattenspiel with contributions from Alun Lloyd PRINCETON UNIVERSITY PRESS PRINCETON AND OXFORD Sattenspielfinal-feb27 February 27, 2009 Copyright (cid:13)c 2009 by Princeton University Press Published by Princeton University Press 41 William Street, Princeton, New Jersey 08540 In the United Kingdom: Princeton University Press 6 Oxford Street, Woodstock, Oxfordshire OX20 1TW All Rights Reserved Library of Congress Cataloging-in-Publication Data Sattenspiel, Lisa. Thegeographicspreadofinfectiousdiseases: modelsandapplications / Lisa Sattenspiel with contributions from Alun Lloyd. p. cm. (Princeton series in theoretical and computational biology) Includes bibliographical references and index. ISBN 978-0-691-12132-1 (hardcover : alk. paper) 1. Communicable diseases–Epidemiology–Mathematical models. I. Lloyd, Alun, 1970- II. Title. III. Series. [DNLM: 1. Communicable Diseases–epidemiology. 2. Communicable Diseases transmission. 3. Disease Outbreaks–statistics & numerical data. 4. Epidemiologic Methods. 5. Models, Theoretical. WA 110 S253g 2009] RA643.S39 2009 614.401’5118–dc22 2008038171 British Library Cataloging-in-Publication Data is available This book has been composed in LATEX The publisher would like to acknowledge the authors of this volume for providing the camera-ready copy from which this book was printed. Printed on acid-free paper. ∞ press.princeton.edu Printed in the United States of America 10 9 8 7 6 5 4 3 2 1 Sattenspielfinal-feb27 February 27, 2009 Dedicated to Steven, Matthew, Elisabeth, and Stephanie who make my life a constant joy and to Franki and Ed (in spirit) who ultimately made this all possible. Love always — Lisa Sattenspielfinal-feb27 February 27, 2009 The formidable task of developing models for endemic disease maybecomparedtobuildingahouseinahurry. Practicalwork- ers insist on building a complete house, and are not too worried thatitmayneedreplacinglater. Theoreticiansinsistonbuilding reliablefoundationsandarenottooworriedifthehouseisnever finished. Both points of view have their merits, and ideally we need to combine these. — Mollison and Kuulasmaa, Spatial Epidemic Models Sattenspielfinal-feb27 February 27, 2009 Contents Preface ix Chapter 1. Introduction 1 1.1 Mathematical Models and the Geographic Spread of Epidemics 5 1.2 Structure of this Book 11 Chapter 2. The Art of Epidemic Modeling: Concepts and Basic Structures 12 2.1 Essential Biological and Epidemiological Concepts 12 2.2 The Cornerstone of Many Epidemic Models — the SIR Model 16 2.3 Demography and Epidemic Models 23 2.4 More Complex Models 25 2.5 The Basic Reproductive Number Revisited 53 Chapter 3. Modeling the Geographic Spread of Influenza Epidemics 58 3.1 A Brief Overview of the Biology of Influenza 58 3.2 Population-based Influenza Models 61 3.3 Individual-based Influenza Models 77 3.4 So What Kind of Model Should One Use to Study Influenza Transmission? 84 Chapter 4. Modeling Geographic Spread I: Population-based Approaches 86 4.1 Spatial Structure and Disease Transmission: Basic Themes 86 4.2 Spatial Modeling Frameworks 89 4.3 Metapopulation Models 90 4.4 Spatially Continuous Models 102 Chapter 5. Spatial Heterogeneity and Endemicity: The Case of Measles 117 5.1 The Persistence and Long-term Cycling of Measles 122 5.2 SpatialHeterogeneity,Synchrony,andtheSpatialSpreadofMeasles 125 Chapter 6. Modeling Geographic Spread II: Individual-based Approaches 134 6.1 Historical Underpinnings of the Use of Networks in Epidemiology 137 6.2 The Nature of Networks 140 6.3 The Language of Network Analysis 142 6.4 Major Classes of Networks 150 6.5 The Influence of Networks on the Dynamics of Epidemic Spread 159 6.6 Theoretical Analysis of Network Models 162 Sattenspielfinal-feb27 February 27, 2009 viii CONTENTS 6.7 The Basic Reproductive Number in Network Models 168 6.8 Infection Control on Networks 171 6.9 Why Aren’t There More Applications of Network Models for Spatial Spread? 173 Chapter 7. Spatial Models and the Control of Foot-and-Mouth Disease 176 7.1 Modeling the Geographic Spread of FMD 180 7.2 The Official Response to the Epidemic and Its Aftermath 185 Chapter 8. Maps, Projections, and GIS: Geographers’ Approaches 191 8.1 Mapping Methods 191 8.2 Identifying Patterns of Disease Diffusion 195 8.3 Epidemic Projections 204 8.4 Detection of Disease Clustering 208 8.5 New and Potential Directions 211 Chapter 9. Revisiting SARS and Looking to the Future 215 9.1 DidMathematicalModelingHelptoStopthe2003SARSEpidemic? 215 9.2 Modeling the Geographic Spread of Past, Present, and Future Infectious Disease Epidemics: Lessons and Advice 223 Bibliography 237 Index 279 Sattenspielfinal-feb27 February 27, 2009 Preface Inearly2002,withthehelpofAlunLloyd,StevenTanner,BenBolker, and Tony Sun, I took on the task of creating a state-of-the-art review ofmodelsforthegeographicspreadofhumaninfectiousdiseases, with particularattentiontothosemodelsthatwereusedforpracticalstud- iesinvolvinglargeepidemiologicaldatasets. Whatwasoriginallycon- ceived of as a substantive review paper (50 pages or so) turned into a 250-page report. That report formed the nucleus for the present book, which has been updated and reorganized to reflect a recent astronomical rise in interest in modeling the geographic spread of in- fectious diseases. Credit for the core of chapters 2, 4, and 6 must go to Alun Lloyd; I mostly provided abundant critiques and revisions to supplement his clear exposition of the technical details related to modeling geographic spread. The majority of the rest of the book is primarily my work, although many of my ideas have been influenced by my numerous discussions with Alun about spatial modeling and its applications. The goal of this book is to introduce how mathematical and com- puter models are used to study the geographic spread of infectious diseases. It is not intended to be a textbook from which one can learn all the relevant mathematical techniques and theory. Rather, it is designed to introduce the reader to the large body of work in this area, to stimulate discussion of the models and applications, and hopefully to generate enough interest in the field to draw new re- searchers to the area and help those already working in mathematical epidemiology to recognize new and interesting problems. The book is not intended to provide an in-depth analysis and review of all models that have been developed to study the geographic spread of infectious diseases. Rather, the focus is on those models that have been used in applications to actual epidemics, which means, of necessity, that many high-quality, but theoretically oriented studies are intentionally omitted from discussion. The primary audience is readers who have background in ecology, epidemiology,humanbiology,andrelatednatural,physical,andsocial sciences, and who have sufficient mathematical background to tackle