Public Health Information Network (PHIN) Series II Outbreak Investigation Methods: From Mystery to Mastery
Access Series Files Onlinehttp://www.vdh.virginia.gov/EPR/Training.asp • Session slides • Session activities (when applicable) • Session evaluation forms • Speaker biographies
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 IISession I “Recognizing an Outbreak”
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 Amy Nelson, PhD, MPH Consultant, NCCPHP Ron Holdway Environmental Health Director, Orange County Health Department, NC Sarah Pfau, MPH Moderator
“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.) • Develop and use a case definition • Apply the process of case finding in an outbreak • Generate a leading hypothesis
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 control” - CDC
Surveillance drives the cycle of public health prevention Surveillance Epidemiologic investigation Prevention measures Applied Targeted Research
Purpose of Surveillance • Assess public health status • Define public health priorities • Evaluate programs • Stimulate research
Surveillance Priority Areas • Frequency • Severity • Cost • Preventability • Communicability • Public interest
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 http://www.vdh.state.va.us/epi/list.asp
Estimate the Magnitude of the ProblemFoodborne disease cases reported in 2003 in VA * Based on 2000 U.S. Census data, per 10,000 people
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
Surveillance data may represent the “tip of the iceberg” True burden of disease depends on several factors Clinical symptoms Medical care seeking behavior Diagnosis Reporting Underreporting in Surveillance
Types of Surveillance • Active vs. passive • Clinician vs. laboratory
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” http://www.vdh.virginia.gov/EPR/Training.asp • Introduction to Public Health Surveillance • Federal Public Health Surveillance • Techniques for Review and Analysis of Surveillance Data
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 • 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.) • Initiate surveillance • Formulate and test hypothesis • Refine hypothesis • Plan additional studies • Implement and evaluate control measures • Communicate findings
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 The case study that will be used in today’s session is based on an outbreak that occurred in Austin, Texas in 1998.
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 Study 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 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 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 • 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 110 minutes Draft Case Report Interview 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 • 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? • File the report and stop? • Investigate further?
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... • 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 • Can’t investigate everything • Often must choose the highest priority • Outside pressure to investigate (media, politicians)
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’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