Epidemiology of Drinking Waterborne and Foodborne Disease

Document Sample
Epidemiology of Drinking Waterborne and Foodborne Disease Powered By Docstoc
					Epidemiology of Drinking Waterborne
      and Foodborne Disease

             ENVR 421
           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
• 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
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
   Pb, NO3, F and Cu       13        394
TOTAL                    87          427,256
    WB Disease Outbreaks 2001-2002
• 31 drinking water OBs reported by
  19 states.
• 1,020 ill persons and seven
• 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
• 5 (20.8%) associated with acute
  chemical poisonings.
    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
  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.
    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.
          “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
                        “Payment Study”, 1991:
   Risks of Gastrointestinal Illness from Tapwater vs. RO-filtered Water

Percent of Study Subjects Reporting HCGI Symptoms and Mean Number of
Episodes per Unit of Observation in Both Periods Combined
                        Filtered Water (n=272)          Tap Water (n=262)
Unit of             % with        Mean Number      % with      Mean Number
Observation         Episodes of Episodesa          Episodes of Episodes
Familey             62.0          3.82             67.7       4.81
Informant           20.0          1.70             23.1       2.10
Youngest child 42.3               1.83             46.3       2.37
aDerived by logistic regression with covariables age, sex, geographic sub-

region. Only subjects who had complete data sets in both periods are
included in this table.
bMean number of episodes among those subjects who reported at least one

                             “Payment Study”, 1991:
    Risks of Gastrointestinal Illness from Tapwater vs. RO-filtered Water
Incidence of HCGI Episodes Derived from Poisson Regression Analysis, by Study
Group for Each of Three Units of Observationa
                              Period 1                              Period 2
Unit of         Filtered    Tap        Preventable Filtered       Tap        Preventable
Observation (n=296)         (n=304)    Fraction (%) (n=262)       (n=276) Fraction (%)
Family          0.65        1.00**     36.0            0.43       0.64**     32.8
Informant       0.64        1.00*      36.0            0.44       0.63*      30.2
Youngest        0.88        1.24*      30.7            0.56       0.80*      30.0
aAnnual incidence per unit of observation, derived by Poisson regression with age, sex,

and subregion in the models.
*Difference between the incidence rates is significant at p<0.05
**Difference between the incidence rates is significant at p<0.01
    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.
  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
• Many experts believe the kitchen is home to
  more potentially dangerous bacteria than even
  the bathroom.
    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.
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
       Salmonella Infection
• Causes an estimated 1.4 million foodborne
• 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.
   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.
FoodNet Surveillance Sites
                   FoodNet Program
                                         Targeted Pathogens:
  Tracks foodborne illness
                                         • Campylobacter
  • surveys of physicians                • E. coli O157
    and laboratories,                    • Listeria
  • case-control studies                 • Salmonella
  • active case finding of               • Shigella
    targeted pathogens                   • Vibrio
                                         • Yersinia
FoodNet Website:
                                         • Cryptosporidium
                                         • Cyclospora
        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.
        Components of FoodNet

•   Active laboratory-based surveillance
•   Survey of clinical laboratories
•   Survey of physicians
•   Survey of the population
•   Epidemiologic Studies
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.
Laboratory Reports of Gastrointestinal Infections in
               England and Wales
Overview of Communicable Diseases
   England and Wales - Priorities

Shared By: