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Epidemiology of Drinking Waterborne and Foodborne Disease

Epidemiology of Drinking Waterborne and Foodborne Disease. ENVR 133 - Lecture 8 Mark D. Sobsey. Pyramid of Water- and Food-borne Disease. Drinking Water‑borne Disease Outbreaks in the U.S. Information comes from reported waterborne outbreaks Based on two or more cases from a drinking water

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Epidemiology of Drinking Waterborne and Foodborne Disease

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  1. Epidemiology of Drinking Waterborne and Foodborne Disease ENVR 133 - Lecture 8 Mark D. Sobsey

  2. Pyramid of Water- and Food-borne Disease

  3. Drinking Water‑borne Disease Outbreaks in the U.S. • Information comes from reported waterborne outbreaks • Based on two or more cases from a drinking water • Data compiled by a passive reporting system to the Centers for Disease Control (CDC), and the Environmental Protection Agency (EPA) for water • Many outbreaks are not noticed or reported • Reported outbreaks are the "tip of the iceberg” • Estimated unreported/unrecognized outbreaks: 50-90% • Etiological agent is not identified or recognized in many outbreaks • The fraction of outbreaks for which an etiological agent is identified had increased in recent years • Etiologic agent is rarely isolated from the incriminated water • Etiologic agent is usually isolated and identified from cases of ill persons

  4. Waterborne Outbreaks in the United States, 1989-1994 Etiologic Agent No. Outbreaks No. Cases Acute GI (unknown) 44 16,264 Cryptosporidium parvum 8 406,822 Giardia lamblia 16 1,205 Hepatitis A virus 4 81 Norwalk-like viruses 1 900 E. coli O157:H7 1 243 Cyclospora cayatenensis 1 21 Shigella spp. 7 570 Salmonella sp. 1 625 Vibrio cholerae (non-01) 1 11 Chemicals: Pb, NO3, F and Cu 13 394 TOTAL 87 427,256

  5. WB Disease Outbreaks 2001-2002 • 31 drinking water OBs reported by 19 states. • 1,020 ill persons and seven deaths. • Microbe or chemical causing OB was identified for 24 (77.4%) of the 31 outbreaks. • Of the 24 identified outbreaks,: • 19 (79.2%) were associated with pathogens • 5 (20.8%) associated with acute chemical poisonings.

  6. WB Disease Outbreaks 2001-2002 • 5 OBs caused by norovirus • 5 OBs by parasites • 3 OBs by non-Legionella bacteria • 6 OBs of Legionnaires disease (LD) • 7 OBs of acute GI illness of unknown etiology suspected of having an infectious cause. • Of the 25 non-Legionella Obs: • 23 (92.0%) in systems using groundwater sources • 9 (39.1%) of these 23 GW ObB were associated with private noncommunity wells not regulated by EPA

  7. Preventing Drinking Waterborne Outbreaks • For surface water supplies, most outbreaks could be eliminated if treatment consisted of proper filtration (including pre‑treatment by coagulation-flocculation) and disinfection. • For groundwater supplies, most outbreaks could be eliminated if proper disinfection was used.

  8. Actual Risk of Enteric Illness in a Drinking Water Supply from a Surface Source: Epidemiological Studies • Payment et al., 1991, 1997 • Laval (Montreal suburb), Quebec, Canada • Drinking water from a sewage-contaminated river source • Water is extensively treated to make drinking water • Compared GI illness rates in two sets (~300 each) of households (four sets in 2nd study): • One set used ordinary tap water • Other set used reverse osmosis filtered water (no pathogens) • 2nd study: also distribution system-tapwater • 2nd study: also treated water bottled at water treatment plant • GI illness rates were about 25-35% (~15% in 2nd study) higher in tap water households • Dose-response relationship: increased illness with increased tap water consumption (glasses/day) • No pathogens were detected in the water • Water met all standards for quality, including coliforms and turbidity.

  9. “Payment Studies”: References • Payment P., et al, (1991). A Randomized Trial to Evaluate the Risk of Gastrointestinal Disease due to Consumption of Drinking Water Meeting Current Microbiological Standards. American Journal of Public Health 81 (6) 703-708. • Payment P., et al (1997). A prospective epidemiological study of gastrointestinal health effects due to the consumption of drinking water. International Journal of Environmental Health Research. 7(1). 1997. 5-31

  10. “Payment Study”, 1991: Risks of Gastrointestinal Illness from Tapwater vs. RO-filtered Water

  11. “Payment Study”, 1991: Risks of Gastrointestinal Illness from Tapwater vs. RO-filtered Water

  12. Foodborne Disease in The USA: 1993-1997 • Bacterial pathogens caused most outbreaks/infections with a known etiology • But, 68% of reported FBDOs were of unknown etiology • Need improved epidemiologic and lab investigations. • ~ 50% had incubations period of >15 hours, suggesting viral etiology. Viruses (e.g., Norwalk-like viruses) are likey a much more important cause of foodborne disease outbreaks than is currently recognized. • Local and state public health lack resources and expertise to diagnose viral pathogens, but the methods are now increasingly available in some state laboratories. • Viral outbreaks are more likely to detected in the future.

  13. Foodborne Disease in the Home • About half of all Salmonella cases result from unsafe handling of food in the home. • Foodborne illness costs the United States $23 billion annually. • Foodborne illness is often mistaken for “the flu, as many of the symptomsa are similar: • stomach pain, diarrhea, nausea, chills, fever, and headache. • Many experts believe the kitchen is home to more potentially dangerous bacteria than even the bathroom.

  14. Foodborne Disease in The USA: 1993-1997 FBDOs with a known etiology: • multistate outbreaks caused by contaminated produce and outbreaks caused by E. coli O157:H7 remained prominent. • S. enteritidis remains a major cause of illness and death. • ~40% of persons who died from S. enteritidis were residents of nursing homes. • Seriousness of S. enteritidis in elderly persons, many of whom might be immunocompromised. • Decrease risks for egg-associated infections of S. enteritidis by not eating raw or undercooked eggs. • Nursing homes, hospitals, and commercial kitchens should use pasteurized egg products for all recipes requiring pooled or lightly cooked eggs. Proper egg storage in homes. • Several outbreaks involved imported food items, emphasizes the role of food production and distribution in FBDOs.

  15. Foodborne Disease Burden in the Unites States • Estimated 76 million illnesses and 5,000 deaths each year. • Foodborne diseases are common, but only a fraction of these illnesses are routinely reported to CDC • Passive surveillance system • Many diseases not reportable • a complex chain of events must occur to report a foodborne infection to CDC • Most household foodborne infection are not recognized or reported

  16. Salmonella Infection • Causes an estimated 1.4 million foodborne illnesses/year • From 1993-1997, only 189,304 Salmonella inections (~38,00/year) reported through the National Salmonella Surveillance System • a passive, laboratory-based system. • In the same period, 357 recognized outbreaks of Salmonella infection resulting in 32,610 illnesses were reported through the Foodborne-Disease Outbreak Surveillance System. • These system greatly underestimate the burden of foodborne disease.

  17. Active Surveillance Network for Foodborne Disease in the United States: FoodNet • Foodborne disease component of the CDC's Emerging Infections Program (EIP). • Established in 1995 • Collaborative project among CDC, several EIP sites (states cities and territories), U.S. Department of Agriculture (USDA), and the U.S. Food and Drug Administration (FDA). • Consists of active surveillance for foodborne diseases and • related epidemiologic studies designed to help public health officials better understand the epidemiology of foodborne diseases in the United States.

  18. FoodNet Surveillance Sites

  19. Tracks foodborne illness using: surveys of physicians and laboratories, case-control studies active case finding of targeted pathogens Targeted Pathogens: Bacteria: Campylobacter E. coli O157 Listeria Salmonella Shigella Vibrio Yersinia Parasites: Cryptosporidium Cyclospora FoodNet Program FoodNet Website: http://www.cdc.gov/foodnet/default.htm

  20. Goals of FoodNet • Describe the epidemiology of new and emerging bacterial, parasitic, and viral foodborne pathogens • Estimate the frequency and severity of foodborne diseases that occur. • Determine how much foodborne illness results from eating specific foods, such as meat, poultry, eggs produce, etc.

  21. Components of FoodNet • Active laboratory-based surveillance • Survey of clinical laboratories • Survey of physicians • Survey of the population • Epidemiologic Studies

  22. Water- and Foodborne Illness Surveillance in Other Countries • Efforts vary from country to country • Most have little if any surveillance • Some have more active and integrated surveillance than in the United States • National health care systems • Integrated laboratories • Subsidized laboratory analyses • Other incentives • political, social, etc.

  23. Laboratory Reports of Gastrointestinal Infections in England and Wales

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