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Water and Infection. Epidemiological Studies Of View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by NORA - Norwegian Open Research Archives WATER AND INFECTION. EPIDEMIOLOGICAL STUDIES OF EPIDEMIC AND ENDEMIC WATERBORNE DISEASE KARIN NYGÅRD Department of Infectious Disease Epidemiology Division of Infectious Disease Control Norwegian Institute of Public Health Oslo 2008 © Karin Nygård, 2008 Series of dissertations submitted to the Faculty of Medicine, University of Oslo No. 664 ISBN 978-82-8072-474-8 All rights reserved. No part of this publication may be reproduced or transmitted, in any form or by any means, without permission. The papers in the attachment in the dissertation are printed in agreement with the respective journals copyright policy or with special permission given by the publishers. Cover: Inger Sandved Anfinsen. Printed in Norway: AiT e-dit AS, Oslo, 2008. Produced in co-operation with Unipub AS. The thesis is produced by Unipub AS merely in connection with the thesis defence. Kindly direct all inquiries regarding the thesis to the copyright holder or the unit which grants the doctorate. Unipub AS is owned by The University Foundation for Student Life (SiO) TABLE OF CONTENTS SUMMARY 6 ACKNOWLEDGEMENTS 8 LIST OF PAPERS 9 LIST OF ABBREVIATIONS 10 1. GENERAL INTRODUCTION 11 WATER AND HUMANS ........................................................................................................................................11 INFECTIOUS AGENTS ASSOCIATED WITH WATER.................................................................................................13 Bacterial infections ...................................................................................................................................................... 13 Parasites ...................................................................................................................................................................... 16 Viruses ......................................................................................................................................................................... 17 THE ROLES OF WATER IN DISEASE TRANSMISSION ..............................................................................................20 Chain of transmission .................................................................................................................................................. 20 The sources and routes of transmission for water-associated infectious agents .......................................................... 20 The portal of entry for water-associated infectious agents .......................................................................................... 21 Emerging challenges.................................................................................................................................................... 22 EPIDEMIC AND ENDEMIC WATERBORNE DISEASE................................................................................................23 Epidemic and endemic disease..................................................................................................................................... 24 Burden of gastrointestinal illness................................................................................................................................. 24 Endemic gastrointestinal illness in Norway................................................................................................................. 27 EPIDEMIOLOGICAL STUDY DESIGNS USED IN INVESTIGATING WATERBORNE DISEASE ........................................29 Cohort study................................................................................................................................................................. 29 Case-control study ....................................................................................................................................................... 30 Ecological study........................................................................................................................................................... 30 Microbial risk assessment............................................................................................................................................ 31 Statistical analysis - the use of regression models ....................................................................................................... 35 SURVEILLANCE OF OUTBREAKS – EPIDEMIC INTELLIGENCE ...............................................................................36 INVESTIGATION OF OUTBREAKS .........................................................................................................................37 Investigation of waterborne outbreaks......................................................................................................................... 39 DRINKING WATER IN NORWAY...........................................................................................................................40 2. BACKGROUND AND OUTLINE OF THE THESIS 42 BACKGROUND....................................................................................................................................................42 SETTING .............................................................................................................................................................42 OUTLINE OF THE THESIS .....................................................................................................................................42 3. AIMS OF THE STUDY 44 PART 1. INVESTIGATING ENDEMIC WATERBORNE DISEASE.................................................................................44 PART 2. INVESTIGATING OUTBREAKS CAUSED BY CONTAMINATED DRINKING WATER .......................................44 PART 3. INVESTIGATING OUTBREAKS CAUSED BY PRODUCE IRRIGATED WITH CONTAMINATED WATER .............45 PART 4. INVESTIGATING AN OUTBREAK CAUSED BY INHALATION OF CONTAMINATED AEROSOLISED WATER ....45 4. MATERIAL AND METHODS 46 PART 1. INVESTIGATING ENDEMIC WATERBORNE DISEASE.................................................................................46 3 Risk factors for campylobacteriosis in Sweden (paper I)............................................................................................. 46 Breaks or maintenance work in water distribution system and gastrointestinal illness (paper II)............................... 46 PART 2. INVESTIGATING OUTBREAKS CAUSED BY CONTAMINATED DRINKING WATER .......................................47 Surveillance of waterborne outbreaks in Norway (paper III). ..................................................................................... 47 Outbreak of giardiasis in Bergen in 2004 (paper IV)................................................................................................... 47 The source of a gastroenteritis outbreak in a summer-camp (paper V) ....................................................................... 49 PART 3. INVESTIGATING OUTBREAKS CAUSED BY PRODUCE IRRIGATED WITH CONTAMINATED WATER .............49 The source of an outbreak of hepatitis A in Sweden (paper VI)................................................................................... 49 The souce of an outbreak of salmonellosis (paper VII)............................................................................................... 50 PART 4. INVESTIGATING AN OUTBREAK CAUSED BY INHALATION OF CONTAMINATED AEROSOLISED WATER ....50 The source of an outbreak of Legionnaires’ disease (paper VIII)................................................................................ 50 STATISTICAL ANALYSIS......................................................................................................................................51 Stratified analysis......................................................................................................................................................... 51 Regression models ....................................................................................................................................................... 52 LABORATORY METHODS ....................................................................................................................................53 Indicators of faecal contamination .............................................................................................................................. 53 Molecular sub-typing methods..................................................................................................................................... 54 ETHICS ...............................................................................................................................................................54 Ethics in outbreak investigations ................................................................................................................................. 54 5. MAIN RESULTS 56 PART 1. INVESTIGATING ENDEMIC WATERBORNE DISEASE.................................................................................56 Environmental risk factors and campylobacteriosis in Sweden (paper I).................................................................... 56 Breaks and maintenance work in the water distribution systems and gastrointestinal illness (paper II)..................... 56 PART 2. INVESTIGATING OUTBREAKS CAUSED BY CONTAMINATED DRINKING WATER .......................................57 Waterborne
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