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Public Health Information Network (PHIN) Series II. Outbreak Investigation Methods: From Mystery to Mastery. Series II Sessions. Access Series Files Online Session slides Session activities (when applicable) Session evaluation forms

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public health information network phin series ii

Public Health Information Network (PHIN) Series II

Outbreak Investigation Methods:

From Mystery to Mastery

access series files online http www vdh virginia gov epr training asp
Access Series Files Online
  • Session slides
  • Session activities (when applicable)
  • Session evaluation forms
  • Speaker biographies
site sign in sheet
Site Sign-in Sheet

Please submit your site sign-in sheet and

session evaluation forms to:

Suzi Silverstein

Director, Education and Training

Emergency Preparedness & Response Programs

FAX: (804) 225 - 3888

series ii session i

Series IISession I

“Recognizing an Outbreak”

session overview
Session Overview
  • Introduction to surveillance
  • Steps of an outbreak investigation
  • Foodborne disease surveillance
  • Case study investigated by Epi Team professionals:

a. Epidemiologists

b. Public Health Laboratory specialists

c. Environmental Health specialists

today s presenters
Today’s Presenters

Amy Nelson, PhD, MPH

Consultant, NCCPHP

Ron Holdway

Environmental Health Director,

Orange County Health Department, NC

Sarah Pfau, MPH


recognizing an outbreak learning objectives
“Recognizing an Outbreak”Learning Objectives
  • Identify multiple types of foodborne illness surveillance systems
  • Recognize uses of surveillance data
  • Identify steps of an outbreak investigation
recognizing an outbreak learning objectives cont d
“Recognizing an Outbreak”Learning Objectives (cont’d.)
  • Develop and use a case definition
  • Apply the process of case finding in an outbreak
  • Generate a leading hypothesis
what is public health surveillance
What is Public Health Surveillance?

“The ongoing, systematic collection, analysis,

and interpretation of health-related data

essential to the planning, implementation, and

evaluation of public health practice, closely

integrated with the timely dissemination of these

data to those responsible for prevention and



Surveillance drives the cycle of public health prevention









purpose of surveillance
Purpose of Surveillance
  • Assess public health status
  • Define public health priorities
  • Evaluate programs
  • Stimulate research
surveillance priority areas
Surveillance Priority Areas
  • Frequency
  • Severity
  • Cost
  • Preventability
  • Communicability
  • Public interest
surveillance applications
Surveillance Applications
  • Estimate the magnitude of the problem
  • Determine the geographic distribution of illness
  • Portray the natural history of a disease
  • Detect epidemics / define a problem
  • Generate hypotheses, stimulate research
  • Evaluate control measures
  • Monitor changes in infectious agents
  • Detect changes in health practice
  • Facilitate planning
va reportable diseases
VA Reportable Diseases

estimate the magnitude of the problem foodborne disease cases reported in 2003 in va
Estimate the Magnitude of the ProblemFoodborne disease cases reported in 2003 in VA

* Based on 2000 U.S. Census data, per 10,000 people

detect epidemics define a problem
Identify baseline for disease

Compare increase with baseline

Eyeball, experience

CUSUM statistical methods

Emerging Infect Dis. 1997; 3(3): 395-400

Detect Epidemics / Define a Problem
underreporting in surveillance
Surveillance data may represent the “tip of the iceberg”

True burden of disease depends on several factors

Clinical symptoms

Medical care seeking behavior



Underreporting in Surveillance
types of surveillance
Types of Surveillance
  • Active vs. passive
  • Clinician vs. laboratory
outbreak surveillance sources
Outbreak Surveillance Sources
  • Laboratory-confirmed reports of notifiable diseases
  • Clinician reports of notifiable disease
  • Concerned parent/citizen reports to health department
  • Media
archived va phin session surveillance
Archived VA PHIN Session:“Surveillance”

  • Introduction to Public Health Surveillance
  • Federal Public Health Surveillance
  • Techniques for Review and Analysis of Surveillance Data
why investigate
Why Investigate?
  • Increase detected through surveillance
  • Characterize the problem
  • Prevention and control
  • Research and answer scientific questions
  • Train epidemiologists
  • Political / legal concerns
cdc guidelines for systematic investigations
CDC Guidelines for Systematic Investigations
  • Verify diagnosis
  • Confirm epidemic
  • Identify and count cases (define)
  • Tabulate and orient data: time, place, person
  • Take immediate control measures
cdc guidelines for systematic investigations cont d
CDC Guidelines for Systematic Investigations (cont’d.)
  • Initiate surveillance
  • Formulate and test hypothesis
  • Refine hypothesis
  • Plan additional studies
  • Implement and evaluate control measures
  • Communicate findings
exceptions to the rule
Exceptions to the Rule
  • CDC guidelines provide a model for systematic outbreak investigations.
  • No two outbreaks are alike!
  • Steps of an outbreak could…
    • occur in a different order
    • occur simultaneously
    • be repeated after new information is discovered
case study
Case Study

The case study that will be used in today’s session is based on an outbreak that occurred in Austin, Texas in 1998.

case study1
Case Study

Today we will review parts of the case study that illustrate how to:

  • Develop and use a case definition;
  • Apply the process of case finding in detecting an outbreak;
  • Verify the diagnosis; and
  • Follow methods for generating a hypothesis.
case study2

Case Study

Disease Surveillance

disease surveillance
Disease Surveillance

On the morning of March 11,1998, the

Texas Department of Health (TDH) received

a telephone call from a male student at a

nearby university

disease surveillance1
Disease Surveillance
  • Student and his roommate were suffering from nausea, vomiting, and diarrhea
    • Both had become ill during the night
    • The roommate had taken medication
    • Neither student sought medical care
    • Both students believed a local pizzeria the previous night was responsible
    • Students asked if they should go to class/take midterm exam that afternoon
disease surveillance case report
Disease Surveillance: Case Report

What questions would you ask the student?

WHO: other ill persons – age, sex, symptoms, and whether they sought care

WHAT: physical condition, symptoms, medication, and medical care sought

WHEN: when did the affected become ill

WHERE: city/school, address, telephone number of ill persons

WHY/HOW: suspected cause of illness, risk factors, modes of transmission, hints from those who did not become ill

case report when how
Case Report:When / How
  • Student refused to provide food history beyond foods
  • eaten at local pizzeria
  • He and his roommate shared no other meals in the last 72
  • hours
  • They ate separately at the University cafeteria
activity 1 10 minutes

Activity 110 minutes

Draft Case Report

Interview Questions

activity 1 possible questions
Activity 1: Possible Questions

WHO: How old are you?

WHAT: What symptoms do you have?

WHEN: What was the first day you began feeling these symptoms?

WHERE: Besides your home, please name each place that you spend time on a regular basis (such as work, school, or another establishment)

WHY / HOW: Let’s go through all of the foods and beverages that you have eaten recently, starting with yesterday. What did you have to eat or drink for breakfast yesterday morning?

disease surveillance advice to the caller
Disease Surveillance: Advice to the Caller
  • What do you advise the student about attending classes that day?
    • Refer to personal clinician or student health center for evaluation
    • If asymptomatic, can return to normal activities
    • Food handler?
    • Work with high risk populations?
disease surveillance what next
Disease Surveillance:What next?
  • File the report and stop?
  • Investigate further?
deciding to investigate
Deciding to Investigate
  • Ideally, all reports of possible food borne outbreaks should be investigated to:
    • Prevent other persons from becoming ill
    • Identify potentially problematic food handling practices
    • Add to the knowledge of food borne diseases
maybe you should
Maybe you should...
  • If a severe (life-threatening) illness
  • If there are confirmed clusters/large numbers of a similar illness
  • If food borne illness is in a food-handler
  • If association with a commercially distributed food
deciding not to investigate
Deciding Not to Investigate
  • Can’t investigate everything
  • Often must choose the highest priority
  • Outside pressure to investigate (media, politicians)
maybe you shouldn t
Maybe you shouldn’t...
  • If signs/symptoms or confirmed diagnoses among the affected suggest they might not have the same illness
  • If ill persons are not able to provide adequate information for investigation, including date and time of onset of illness, symptoms, or a complete food history
maybe you shouldn t1
Maybe you shouldn’t...
  • If confirmed diagnosis and/or clinical symptoms are not consistent with the foods eaten and the onset of illness
  • If there are repeated complaints made by the same individual(s) for which prior investigations revealed no significant findings
case study3

Case Study

Case Finding

case definition
Case Definition

To verify the existence of an outbreak, you must establish that a higher number of cases than expected is occurring.

case definition1
Case Definition

A standard set of criteria for deciding whether an individual should be classified as having the disease of interest, including:

  • Clinical criteria (signs, symptoms, and laboratory tests)
  • Restrictions on person, place, and time
case definition2
Case Definition
  • The case definition can be modified as more data are obtained
  • Do not include the hypothesis being tested in the case definition
tx case study case definition
TX Case StudyCase Definition:

Initial Case Definition:

“University student with diarrhea and vomiting in the previous 24 hours”

activity 2

Activity 2

Develop a Case Definition

activity 2 case definition
Activity 2: Case Definition

Cases are adults living in Jonesville, USA, diagnosed with laboratory confirmed E. coli 0157:H7 at the end of October, or having symptoms (abdominal cramping, bloody diarrhea) compatible with this diagnosis at this time without laboratory confirmation.

case finding using the case definition
Case Finding: Using the Case Definition
  • Look for more cases (student health center, hospitals, clinicians, dorm rooms) to determine the extent of the potential outbreak
case finding
Case Finding
  • The pizzeria where the student and roommate had eaten was closed until 11:00 A.M.
  • There was no answer at the University Student Health Center (left a message on the answering machine)
case finding1
Case Finding
  • A call to the emergency room at a local hospital revealed that 23 university students had been seen for acute gastroenteritis in the last 24 hours
  • In contrast, only three patients had been seen at the emergency room for similar symptoms from March 5-9, none of whom were associated with the university
case finding2
Case Finding
  • At 10:30 A.M., a student health center physician returned the call and reported that 20 students with vomiting and diarrhea had been seen the previous day (no stool specimens were collected)
  • The physician reported that 1-2 students per week typically would have been seen for these symptoms
outbreak detection is this an outbreak
Outbreak Detection: Is This an Outbreak?

Definition of an outbreak

The occurrence of more cases of a disease than expected for a particular place and time

  • Expected # of cases: ~5 per week
  • Actual # of cases: 40+ per day

Outbreak detected?


prospective case finding
Prospective Case Finding
  • TDH staff asked local health care providers to report cases of vomiting or diarrhea seen since March 5 at the:
    • University Student Health Center
    • Hospital A emergency room
    • Emergency departments at six other hospitals located in the general vicinity
  • Health care providers were asked to collect stool specimens from any new cases
case finding descriptive epidemiology
Case Finding:Descriptive Epidemiology
  • Afternoon of March 11, TDH staff visited the emergency room at Hospital A and reviewed medical records of patients seen for vomiting and/or diarrhea since March 5
  • Symptoms among 23 university students seen included:
    • Oral temperatures ranged from 98.8/F (37.1/C) to 102.4/F (39.1/C)
    • Complete blood counts showed an increase in white blood cells (n=10)
case study4

Case Study

Verify the Diagnosis

verify the diagnosis microbiology
Verify the Diagnosis: Microbiology
  • What broad categories of diseases might be causing the outbreak?
    • Enteric viruses
    • Bacteria
    • Parasites
    • Toxins
  • Stool specimens had been submitted for routine bacterial pathogens, but no results were available
verify the diagnosis microbiology1
Verify the Diagnosis: Microbiology
  • A TDH staff person was designated to help the facilities identify and report cases
  • Bacterial cultures from patients seen in the emergency rooms were performed at the collecting hospital and confirmed at the TDH Laboratory
  • Specimens collected by the Student Health Center were cultured at the TDH Laboratory
verify the diagnosis find plausible agents
Verify the Diagnosis: Find Plausible Agents


  • Predominant signs and symptoms
  • Incubation period
  • Duration of symptoms
  • Suspected food
  • Laboratory testing of stool, blood, or vomitus
verify the diagnosis find plausible agents1
Verify the Diagnosis: Find Plausible Agents
  • Pathogen identification will help identify the potential incubation period
  • Crucial to know the incubation period for hypothesis generation
  • Don’t need to wait for laboratory diagnosis to proceed
epidemiological profiling
Epidemiological Profiling

Epidemiol Infect. 2001;127:381-7

epidemiological profiling1
Epidemiological Profiling
  • Case Study chart review results (N=23)
    • Vomiting = 90%
    • Fever = 67%
    • Vomiting / Fever =1.34
    • Median duration = 39 hours
epidemiological profiling2
Epidemiological Profiling

Kaplan criteria for Norovirus outbreak:

  • Incubation period 24 to 48 hrs
  • Duration of illness 12 to 60 hrs
  • Vomiting >50% of cases
  • Modified to include vomiting/fever > 1.0
  • Negative for other pathogens
pathogen identification resource
Pathogen IdentificationResource

CDC’s Foodborne Outbreak Response and Surveillance Unit

“Guide to Confirming the Diagnosis in Foodborne Diseases”

pathogen identification
Pathogen Identification

  • Norwalk Virus
  • Group of related,

SS RNA non-

enveloped viruses

  • Cause acute gastro-

enteritis in humans

  • The estimated total cases of Norovirus infection is 23,000,000 in the U.S. per year.
  • Approximately 40% of Norovirus infections are food borne.
  • Noroviruses are responsible for 67% of the total food borne infections, 32 % of the hospitalizations and 7% of the deaths.
clinical presentation
Clinical Presentation
  • Incubation period is usually 24-48 hours
  • Acute onset vomiting
  • Watery, non-bloody diarrhea with abdominal cramps
  • Nausea
  • Low-grade fever may occur
clinical presentation con t
Clinical Presentation (Con’t)
  • Dehydration is the most common complication, especially among the young and the elderly
  • Symptoms usually last between 24 to 60 hours
  • Recovery is usually complete and there is no evidence of long term complications
  • Asymptomatic infection may occur in as many as 30% of the infected
treatment and management
Treatment and Management
  • No specific therapy exists for viral gastroenteritis
  • Standard symptomatic therapy consists of replacing fluid losses and correcting electrolyte imbalances through oral and intravenous fluid administration
virus transmission
Virus Transmission
  • Noroviruses are transmitted primarily through the fecal-oral route via fecally contaminated food or water or by direct person-to-person spread
  • Fomite contamination may also act as a source of infection
  • Aerosolization of vomitus may spread the virus but not through the respiratory system
virus transmission con t
Virus Transmission (Con’t)
  • Noroviruses are highly contagious – an inoculum of as few as 10 viral particles may be sufficient
  • Shedding usually begins with the onset of symptoms (although there may be some pre-symptom shedding) and may continue for two weeks after recovery
specimen collection
Specimen Collection
  • Human: Identification can best be made from stool specimens taken within 48-72 hours after the onset of symptoms. Vomitus and serum may also be collected and tested
  • Environmental: Food and water samples can be collected and tested. Water samples should be filtered to increase the concentration of virus present
  • Not part of the routine lab culture work-up for gastroenteritis
forensic specimens
Forensic Specimens
  • Public health specimens as evidence in criminal investigations
    • Samples taken as part of a legitimate investigation of an outbreak or other public health situation may be used in a criminal investigation
    • Chain of custody: form documenting dates and person / entities having the evidence (specimen) in their custody (i.e. for collection or transport)

Prevention is based on:

  • The provision of safe food and water
  • Correct handling of cold foods
  • Frequent hand washing
  • Paid sick leave
case study5

Case Study

Back to Verifying the Diagnosis. . .

verify the diagnosis culture results
Verify the Diagnosis: Culture Results

Later in the afternoon of March 11th, culture

results from 17 ill students became available

verify the diagnosis culture results1
Verify the Diagnosis: Culture Results
  • Results were primarily from the emergency room at Hospital A on March 10
  • Results did not identify Salmonella, Shigella, Campylobacter, Vibrio, Listeria, Yersinia, Escherichia coli O157:H7, Bacillus cereus, or Staphylococcus aureus
  • Some specimens were positive for fecal leukocytes and fecal occult blood
microbiology diagnosis interpretation of results
Microbiology Diagnosis:Interpretation of Results

What do these results mean, and what

questions do they raise?

microbiology diagnosis interpretation of results1
Microbiology Diagnosis:Interpretation of Results
  • Potential reasons for negative results:
    • Mishandling of specimen resulting in death of the pathogen (during storage, transport, processing, or culture)
    • Specimens collected too late in the illness
    • Illness could be due to a bacteria not tested for, or due to a non-bacterial agent
case study6

Case Study

Hypothesis Generation

hypothesis generation
Hypothesis Generation

Day 2 (March 12)…

  • 75 persons with vomiting or diarrhea reported
  • All were university students who lived on campus
  • No cases among faculty or staff, or locals
  • Medianpatient age 19 years (range: 18-22)
  • 69% were freshman
  • 62% were female
hypothesis generation line listing
Hypothesis Generation:Line Listing

This line listing has been sorted on the “Age” data field.

hypothesis generation epidemic curve
Hypothesis Generation:Epidemic Curve

Viral incubation: Average = 24-48 hours

Range = 1 – 7 days

hypothesis generation meet with university officials
Hypothesis Generation:Meet with University Officials
  • Negotiate cooperation with the university officials
  • Inform, update, plan, and coordinate
hypothesis generation meet with university officials1
Hypothesis Generation:Meet with University Officials

Collect information that might provide insights into the source of the outbreak, including:

  • Characteristics of the student body
  • Sources of food/water, dining establishments
  • Possible contact with animals through classes
  • Student living arrangements
hypothesis generation information collected
Hypothesis Generation: Information Collected
  • The university is located in a small Texas town with a population of 27,354
  • Enrollment of approximately 12,000 students
  • 2,386 students live on campus
    • 36 residential halls on the 200+ acre main campus
    • Most enrolled in on-campus meal plan
  • About 75% of the students are Texas residents
hypothesis generation information collected1
Hypothesis Generation:Information Collected
  • The university uses municipal water and sewage services
  • There have been no breaks or work on water or sewage lines in the past year
  • There has been no recent road work or digging around campus
hypothesis generation information collected2
Hypothesis Generation:Information Collected

Main cafeteria

  • Used by most on campus students
  • Serves hot entrees, as well as items from the grill, deli bar, and a salad bar
hypothesis generation information collected3
Hypothesis Generation:Information Collected

Smaller cafeteria

  • Used by students who live off campus and university staff
  • Also serves hot entrees, grilled foods, and a salad bar, but has no deli bar
  • Offers menu selections with a per item cost
  • Accessible to meal plan members
hypothesis generation information collected4
Hypothesis Generation:Information Collected
  • Both cafeterias under same management
  • Also about half a dozen fast food places on campus
hypothesis generation information collected5
Hypothesis Generation:Information Collected
  • Spring break begins on March 13, at which time all dining services will cease until March 23
  • Many students will leave town during the break, but about 25% of those living on campus will remain
hypothesis generation case interviews
Hypothesis Generation:Case Interviews

Hypothesis generating interviews were done with seven of the earliest case-patients reported by the ER and student health center

hypothesis generation case interviews1
Hypothesis Generation: Case Interviews
  • All 7 cases had onset of illness on March 10
  • Four were male and three were female
  • All but one was a freshman
  • Two students were psychology majors; one each was majoring in English and animal husbandry. Three students were undecided
hypothesis generation case interviews2
Hypothesis Generation: Case Interviews
  • Except for the psychology majors, none of the other students shared any classes
  • Only one student had a roommate with a similar illness
  • Lived in five different residential halls
hypothesis generation case interviews3
Hypothesis Generation: Case Interviews
  • Five students belonged to a sorority or a fraternity
  • Three students had attended an all school mixer on March 6, the Friday before the outbreak began
hypothesis generation case interviews4
Hypothesis Generation: Case Interviews
  • Two students went to an all night science fiction film festival at one of the dorms on March 7
  • Students reported attendance at no other special events; most had been studying for midterm exams for most of the weekend
hypothesis generation case interviews5
Hypothesis Generation: Case Interviews

Seven day food history:

  • All reported eating most of their meals at the university’s main cafeteria
  • All but one student had eaten food from the deli bar
  • Two had eaten food from the salad bar
  • Three from the grill
  • Only one had eaten food from the pizzeria
  • No particular food item that was common to all or most of the students
hypothesis generation2
Hypothesis Generation

What are your leading hypotheses for the cause of the outbreak?


  • Pathogen
  • Mode of transmission
  • Source of outbreak
  • Time period of interest (incubation)
hypothesis generation 1 pathogen
Hypothesis Generation:1. Pathogen
  • Signs and symptoms (vomiting, diarrhea, fever, bloody stools, fecal leucocytes, and fecal occult blood) consistent with acute gastrointestinal infection
  • Negative bacterial cultures suggest a viral or parasitic pathogen
  • Symptoms more consistent with virus
hypothesis generation 1 pathogen1
Hypothesis Generation:1. Pathogen

Epi Curve suggests a point source outbreak and short exposure period

More consistent with a virus than parasite

hypothesis generation 2 mode of transmission
Hypothesis Generation: 2. Mode of Transmission
  • Illness is limited to students living on campus
  • Lack of illness in community, faculty, suggests city or university water systems not affected
hypothesis generation 2 mode of transmission1
Hypothesis Generation: 2. Mode of Transmission
  • Not spread person-to-person
    • Cases did not cluster by dorm or classes
  • All 7 students ate at university main cafeteria and deli bar
    • Not used by off-campus students or faculty
hypothesis generation 3 source
Hypothesis Generation: 3. Source
  • No common food items identified among 7 students
  • Viral agents are commonly transmitted through
    • Sandwiches
    • Salads
    • Raw / undercooked shellfish
hypothesis generation 4 period of interest
Hypothesis Generation: 4. Period of Interest
  • Viral gastroenteritis
    • Incubation ranges <1day to ~7 days
  • Majority of onset
    • March 10 – 12
  • Likely exposure period
    • March 5 – 10
    • (<1 to 7 days before case onset)
hypothesis generation3
Hypothesis Generation

Leading Hypothesis:

Viral infection spread by a food or beverage served at the university main cafeteria between March 5 and March 10

activity 3

Activity 3

Generate a Leading Hypothesis

activity 3 leading hypothesis
Activity 3: Leading Hypothesis

Option “B” is correct:

Exposure to E. coli O157:H7 occurred through juice served at the local gym in late October.

what next
What Next?
  • Have you proven your hypothesis?
    • No!
    • Information suggests, but does not prove, that the cause of the outbreak was in the main cafeteria
  • Can control measures be taken?
    • Not yet
what next1
What Next?

Next Steps:

  • Environmental investigation
  • Conduct a controlled study
case study7

Case Study

Back to the Texas case study environmental investigation. . .

environmental investigation conduct interviews
Environmental Investigation:Conduct Interviews
  • TDH environmental sanitarians inspected the main cafeteria and interviewed staff on March 12
  • Except for one employee who worked at the deli bar and declined to be interviewed, all dining service personnel were interviewed
environmental investigation food handler interviews
Environmental Investigation:Food Handler Interviews

Topics to cover:

  • Food items served during the implicated time period
  • Illness among staff or their family members during the time period
  • Hygienic practices and hand washing facilities
  • Stool specimens from food handlers
environmental investigation food handler interviews1
Environmental Investigation:Food Handler Interviews

Topics to cover:

  • Watch/reconstruct food preparation/ handling practices performed during the time period
  • Which staff were responsible for what during the time period
  • Recipes for food items served, ingredients and their sources
environmental investigation food handler interview results
Environmental Investigation: Food Handler Interview Results
  • Thirty-one staff members were employed at the cafeteria
    • 24 (77%) were food handlers
  • No food handlers interviewed reported being ill in the last two weeks
  • Stool cultures were requested from all cafeteria staff
environmental investigation food handling practices observed
Environmental Investigation:Food Handling Practices Observed
  • In the cafeteria, the deli bar had its own preparation area and refrigerator
    • Sandwiches were made to order by a food handler
    • Newly prepared deli meats, cheeses, and condiments were added to partially depleted deli bar items from the day before (without discarding leftover food items)
    • While the deli was open, sandwich ingredients were not kept refrigerated. The deli bar containers were not routinely cleaned
environmental investigation sampling
Environmental Investigation: Sampling
  • Samples of leftover food, water, and ice were collected
environmental investigation evidence based decision
Environmental Investigation:Evidence-Based Decision

By dinner on March 12, the City Health

Department closed the deli bar

environmental investigation points to consider
Environmental Investigation:Points to Consider
  • Do you agree with the decision to close the deli bar?
    • Circumstantial evidence only
    • Many unsafe practices identified
  • What do you think the next step should be?
today s conclusions
Today’s Conclusions:
  • We detected an outbreak of viral gastroenteritis
  • We developed a leading hypothesis with the main campus cafeteria as the suspect
environmental investigation

Environmental Investigation

Ron Holdway

Environmental Health Director Orange County Health Department, North Carolina

orange county health department dr rosemary summers director



orange county health department



January 2004

the unc outbreak
The UNC Outbreak
  • Background
  • Questions and Issues
  • Environmental Investigation and Control Measures
  • Final Analysis / Results
the unc outbreak background
The UNC OutbreakBackground
  • Call from UNC Student Health on January 21st – AM
  • A few cases (4-6) presented on 1-20
  • Many more (50-60) presented on 1-21
  • OCHD Epi Team convened at UNC SHS office
the unc outbreak background1
The UNC OutbreakBackground
  • Epi Team Work on 1-21
    • Understanding of situation (easier said than done!)
    • Met with UNC SHS and EHS representatives
    • Met with food service representatives
    • Consulted with State epi representatives
    • Alert/query to private providers in the community
    • Outbreak (epidemic) or not? (YES!)
    • Limited to UNC universe? (Yes)
    • Case definition
the unc outbreak background2
The UNC OutbreakBackground
  • Epi Team Work on 1-21 (cont.)
    • Possible agents and transmission modes
    • Questionnaire development & testing
    • Administer questionnaire (began that night around 8pm after testing)
    • Implemented general control measures
    • Interviews with press representatives
    • Some food samples
    • At least one vomitus sample
the unc outbreak background3
The UNC OutbreakBackground
  • Case Definition
    • “A UNC student with an acute episode of nausea, vomiting and/or diarrhea with onset on or after 6PM on 1-20-04”
the unc outbreak background4
The UNC OutbreakBackground
  • Possible Agents
    • Based on signs, symptoms and those that occur first or predominate - vomiting was occurring first and appeared to be predominating in this outbreak
    • Sudden or gradual increase in cases?
the unc outbreak background5
The UNC OutbreakBackground
  • Possible Agents (cont.)
    • Among those considered for this outbreak:
      • Bacillus cereus toxin
      • Staphylococcal aureus toxin
      • Norovirus
      • Metal or other elemental poisoning
      • Fish and shellfish toxins
the unc outbreak2
The UNC Outbreak

Questions and Issues

the unc outbreak questions and issues
The UNC OutbreakQuestions and Issues
  • Point source or not?
  • Contained to UNC?
  • Intentional?
  • Questionnaire and study
  • Snow storm during event
the unc outbreak questions and issues1
The UNC OutbreakQuestions and Issues

Point Source or Not?

  • Time, place, person associations
  • Epi curve(s) - we reviewed the numbers of cases at least daily
  • Surveillance and disease presence in the general population
    • ED
    • Private providers
    • PHRST Team
the unc outbreak questions and issues2
The UNC OutbreakQuestions and Issues


  • Don’t discount until investigation and analyses are complete
    • Even then . . . there is the case from The Dalles, Oregon
  • Many agents aren’t conducive to intentional releases
  • Considered but discounted for this outbreak
the unc outbreak questionnaire and study
The UNC OutbreakQuestionnaire and Study
  • Case-control study
  • Obtain well interviews from sick contacts (room mates, suite mates, etc.)
  • Initial software was spreadsheet, but was changed to Epi Info
the unc outbreak questionnaire and study1
The UNC OutbreakQuestionnaire and Study
  • Food histories (at least 48 hours prior) - on-campus and off
  • Contacts
  • Other environmental exposures
    • Vomitus
    • Dorms
    • Travel
    • Swimming pools
the unc outbreak questionnaire and study2
The UNC OutbreakQuestionnaire and Study
  • Obstacles, Problems and Lessons Learned
    • Vast array of foods at UNC dining halls
    • Study was designed to get controls from contacts of sick - this approach was flawed
    • Data from multiple inputs stations could not be merged by OCHD - problem finally solved by Drew Voetsch
the unc outbreak3
The UNC Outbreak

Environmental Investigation and Control Measures

(Those used or considered)

the unc outbreak environmental investigation and control measures
The UNC OutbreakEnvironmental Investigation and Control Measures
  • Dorm sweeps
  • Interviews
  • SHS waived after hours fees
  • UNC installed waterless hand sanitizer
  • stations in the dining halls
  • Cleaning supplies were made available in the dorms through the RAs
the unc outbreak environmental investigation and control measures1
The UNC OutbreakEnvironmental Investigation and Control Measures


  • Student emails and web postings
  • Hand wash posters and signs
  • UNC, State Epi and County officials
  • Advisories to housekeeping staff
  • Press
the unc outbreak environmental investigation and control measures2
The UNC OutbreakEnvironmental Investigation and Control Measures
  • Environmental investigations / interventions
    • Water line work on campus in the last two weeks?
    • Chemical transportation in the last week?
    • Increased fomite cleaning
    • Vomitus control
  • Once food and locations was suspected (1-22), close the facility or not?
the unc outbreak environmental investigation and control measures3
The UNC OutbreakEnvironmental Investigation and Control Measures
  • Sampling through two labs (SLPH and UNC SPH)
    • Food (facility keeps samples for one week)
    • Stool
    • Vomitus
  • Review of food operations and procedures
  • Assessment of connection to other concurrent outbreaks in the region
the unc outbreak environmental investigation and control measures4
The UNC OutbreakEnvironmental Investigation and Control Measures
  • Once food and location were suspected (1-22), close the facility or not?
    • On-going outbreak? (No)
    • Extensive problems discovered during operational review? (No)
the unc outbreak4
The UNC Outbreak

Investigation Analysis / Results

the unc outbreak analysis results
The UNC OutbreakAnalysis / Results
  • Duration - Jan. 20th thru Feb. 13th
  • Total Cases - Suspected and Confirmed - 425 Persons
  • Agent was norovirus
  • Statistically linked to the salad bar at one dining hall
  • Could not link to a specific food item
the unc outbreak analysis results1
The UNC OutbreakAnalysis / Results
  • Primary outbreak was point-source
  • Many secondary cases - person-to-person and environmental exposure
the unc outbreak5
The UNC Outbreak

SOURCE: Drew Voetsch, UNC-CH

stay tuned for the next two sessions
Stay Tuned for The Next Two Sessions. . .

In July we will:

  • Discuss risk communication methods and strategies to use during outbreak investigations

In August we will:

  • Develop a study design to test the Texas case study leading hypothesis
  • Determine what evidence we need to act on the leading hypothesis
next session july 7th 1 00 p m 3 00 p m

Next Session July 7th1:00 p.m. – 3:00 p.m.

Topic: “Risk Communication”

access series files online http www vdh virginia gov epr training asp1
Access Series Files Online
  • Session slides
  • Session activities (when applicable)
  • Session evaluation forms
  • Speaker biographies
site sign in sheet1
Site Sign-in Sheet

Please submit your site sign-in sheet and

session evaluation forms to:

Suzi Silverstein

Director, Education and Training

Emergency Preparedness & Response Programs

FAX: (804) 225 - 3888

references and resources
References and Resources
  • FOCUS Workgroup. An Overview of Outbreak Investigations. FOCUS on Field Epidemiology (1):1.
  • FOCUS Workgroup. Anatomy and Physiology of an Outbreak Investigation Team. FOCUS on Field Epidemiology (1):2.
  • Hall, J.A., et al. Epidemiologic profiling: evaluating foodborne outbreaks for which no pathogen was isolated by routine laboratory testing: United States, 1982-9. Epidemiol Infect. 2001;127:381-7
references and resources1
References and Resources
  • Nelson, A. Embarking on an Outbreak Investigation. FOCUS on Field Epidemiology (1):3.
  • The North Carolina Center for Public Health Preparedness. Outbreak Investigation Training website:
  • Torok, M. Case Finding and Line Listing: A Guide for Investigators FOCUS on Field Epidemiology (1):4.