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Unhappy Camping

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					  Unhappy Camping
   Unhappy Camping
  Investigation of a
   A multipathogen outbreak
Multipathogenoutbreak
  Can we blame it on the water?
              The Initial Calls
• May 24, 2005
  – EH manager of LHD notified by acquaintance of illness
    among 7th graders
• May 25th 2005
  – GI illness among 7th graders who attended outdoor
    school May 17-21 reported to appropriate LHD
  – A regional Oregon lab reports detecting shiga-toxin
    producing E.coli in a student who attended the camp
  – Camp activity director confirms that many campers
    have been ill
            The Investigation
• May 26, 2005              • May 27, 2005
  – Site visit by epi,        – Cohort study of
    environmental health,       campers, parents, staff
                                 • Telephone
    food safety                    Questionnaire
  – Water and sanitary               –   Meals
    survey                           –   Activities
                                     –   Symptom profiles
  – Lab queries                      –   Specimen requests
  – Questionnaire             – Camp closed for
    developed                   weekend “voluntarily”
        Cohort Study Results
99 (84%) of 117 camp attendees interviewed
                    Ill=60    Well=39

   Female          33 (55%)   20 (51%)

   Age yrs          19/12      29/13
   (mean/median)
   Age Range        10-63      11-78
Symptom profiles of Ill campers

     Symptom           Number (%)
     Diarrhea          56 (100%)
      Cramps            48 (82%)
>3 Loose stools/24hr    45(80%)
       Fever            29 (52%)
   Bloody stool         17 (30%)
Onset of Illness, Camp Z


                       Enteric Pathogens
                       E.coli O157 =9
                       E.coli 0145=2
                       Campy sp=3
                       O157&Campy=3




  Camp
  Case Definitions, Analytic Plan
• Primary Case definition
   – Onset of diarrhea after May 17th in person attending
     Camp Z outdoor school (cases=60, controls=38, excluded=1)
• Other Case definitions
   – Lab confirmed E. coli O157 (cases=12, controls=40,
     excluded=47)
   – Labs confirmed E.coli O157 or O145 or Campylobacter
     sp (cases=17, controls=40, excluded=42)
• Analytic Plan
   – >100 variables, 3 case definitions
   – p <0.01 considered significant
       Risk Factors for Illness
• Team-building activities (Nitro crossing,
  Wilderness crossing) associated with lab
  confirmed E.coli 0157
• No association of illness with age, sex,
  activity group, cabin, outdoor school
  activities, meal items, water or drink
  consumption
“Wilderness Crossing”
“Nitro Crossing”
   Environmental Microbiology
May 26, 2005, a sunny day, counts per 100 ml
Specimen        Coliforms       E. coli
Raw water         649            19
Treated water absent            absent

          Sanitary Survey
No water supply and sanitary drains cross connection
No leakage from drain fields
       Food Safety Inspection
• Food supply
  – Prepackaged, minimal preparation
• No illness among full-time kitchen staff of 4
• Food served “family style” with assistance
  by students and parents
  – “Mandatory” glass of water for everyone before
    food could be eaten
Camp Topography
Camp Stream Flow




               Stream Flow
Drain Fields




                             Septic
                             Drain
                             Fields
               Stream Flow
Water Intake for Camp Treatment Plant

                        Water Intake




                                    Septic
                                    Drain
                                    Fields
                      Stream Flow
Sand Filter           Chlorination
Pressure Tank
                DE Filter
Rainfall and Turbidity of treated water
                 0.7                                                             1.6


                 0.6                                                             1.4
                            Precipitation(inches)
                            Turbidity of Treated Water                           1.2
Inches of rain




                 0.5

                                                                                 1
                 0.4




                                                                                       NTU
                                                                                 0.8
                 0.3
                                                                                 0.6

                 0.2
                                                                                 0.4

                 0.1
                                                         Camp                    0.2

                  0                                                              0
                       14-May 15-May 16-May 17-May 18-May 19-May 20-May 21-May

                                                     Date
 Water disinfection variables

Factor              Best disinfection if:   On May 18

Temperature                 higher            9.9 Co

pH                          lower              6.42

Turbidity                   lower            >1 NTU

Chlorine residual           higher           .32 ppm

Contact time                longer           175 min
 Water disinfection variables

Factor              Best disinfection if:   On May 18

Temperature                 higher            9.9 Co

pH                          lower              6.42

Turbidity                   lower            >1 NTU

Chlorine residual           higher           .32 ppm

Contact time                longer           175 min
                                                27 min
  A direct link to stream water ?
• June 2005
  – 6 gallons raw water
    collected during
    rainstorm
  – Many E. coli but no
    O157, O145, or
    Campylobacter isolated
 Is the drinking water a plausible
              source?
• Surface water is a challenging source
  – worse after rainfall
• Water treatment plant equipment was
  substandard, operator untrained
• Diatomaceous earth filtration ineffective
• Incorrect chlorine contact time estimate
• Multiple pathogens, high attack rate
• No other plausible risk factors identified
 No Analytic evidence for water
         as risk factor
• Near universal exposure
• Why did dose response
  questions fail?
   – Not carefully asked (mea
     culpa)
   – Interviews conducted 7-
     12 days after exposures
   – 80% of attendees were
     age 12 or under
   Surveillance of outbreaks of waterborne
   infectious disease: categorizing levels of
                   evidence
       Tillett, Louvois, Wall Epidemiol Infect 1998; 120:37-42

• A= pathogen found in              Level of Evidence
  water                             Strong: A+C or A+D or
• B=water quality failure,            B+C
  pathogen not found in
  water                             Probable: B+D or A only
• C=Analytic association            Possible: B only or D
  of water an illness
                                      only
• D=Descriptive epi
  suggests water is
  source and excludes
  other explanations
New Slow Sand Filters
               Collaborators

Oregon Acute and        Oregon Public Health Lab
Communicable Disease      Larry Staufer
  June Bancroft           Rob Vega
  Julie Hatch           Institute for Environmental
  Melissa Plantenga        Health (Seattle)
                          Mansour Samadpour
  Paul Cieslak
                          Greg Ma
  Stephen Ladd-Wilson
                        Yamhill County Health Dept
  Mel Kohn
                          Gary Vanderveen
Oregon Drinking Water     Matt Jaqua
  Dave Leland             Bob Moore
  Tom Charboneau        Yellowstone National Park
                          William E. Keene
      The setting and the event
• 210 acre residential    • May 17-21, Outdoor
  Christian camp in         School
  northern Oregon           – 5 Christian Academies in
• Sleeping capacity 300       Oregon
• >10,000 visitors/yr          • 80 students
                               • 17 outside staff
• Activities
                               • 20 parents
   – Summer camps
                            – Outdoor school
   – Outdoor schools
   – Special events         – Challenge Course
                            – Meals
             Interventions
• Camp Closed briefly during investigation
• Re-opened next week using water trucked
  from nearby municipal source
• Slow sand filters installed
• Residual chlorine levels increased
• Contact time study done

				
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posted:4/14/2010
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