1. Epidemiology of Drinking Waterborne and Foodborne Disease
ENVR 421
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) ,264
Cryptosporidium parvum ,822
Giardia lamblia ,205
Hepatitis A virus
Norwalk-like viruses
E. coli O157:H
Cyclospora cayatenensis 1 21
Shigella spp
Salmonella sp
Vibrio cholerae (non-01) 1 11
Chemicals:
Pb, NO3, F and Cu
TOTAL ,256

14. WB Disease Outbreaks
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.

15. 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

16. 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.

17. 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.

18. “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)
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)

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

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

33. 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.

34. 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.

35. 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.

36. 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

40. Salmonella Infection
Causes an estimated 1.4 million foodborne illnesses/year
From , 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.

44. 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.

45. FoodNet Surveillance Sites

46. FoodNet Program Tracks foodborne illness using:
Targeted Pathogens:
Bacteria:
Campylobacter
E. coli O157
Listeria
Salmonella
Shigella
Vibrio
Yersinia
Parasites:
Cryptosporidium
Cyclospora
Tracks foodborne illness using:
surveys of physicians and laboratories,
case-control studies
active case finding of targeted pathogens
FoodNet Website:

47. 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.

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

49. 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.

50. Laboratory Reports of Gastrointestinal Infections in England and Wales

51. Overview of Communicable Diseases England and Wales - Priorities