1. Outbreak Investigation
Dr Ghazi Sharkas
Jordan FETP ( )

2. How outbreaks are recognized
The occurrence of an unusual disease, or an unusual number of cases of a disease
By revision of the ordinary surveillance data
By the patients or their relatives
Rumors
Some outbreaks are recognized through newspapers, television news, or Police departments

3. Why to investigate an outbreak
Uncover a much more serious public health problem
Identify risk factors associated with infection under study, that can be preventable

4. Why to investigate an outbreak
Cont…
Increasing knowledge of disease:
Help Preventing future outbreaks
Provide a base line for research about the disease under investigation
Opportunities for training of health staff on problem investigation and rapid response

5. What to do after outbreak detection
Epidemiological investigation
Environmental investigations
Interaction with the public, the media and sometimes the legal authorities

6. Epidemiological outbreak investigation steps

7. 1. Confirm the existence of the outbreak
Compare with
Baseline surveillance data
Data from local sources, neighboring areas or national data
lab diagnosis of the pathogen
Apply immediate control measures if the source is obviously defined

8. 2. Verify the diagnosis Rule out laboratory error
Interview / examine case patients
Review medical records

9. 3. Prepare for field work Compose a team and distribute roles
Put an action plan
Take all required facilities
Ice bags
Necessary lab utensils
Laptop
Sample questionnaires
Other supplies

10. 4. State a case definition
using
Symptoms or lab results
When (time frame)
Who's affected (person)
Where (place)
Categorize case definition, suspected, probable, confirmed

11. 5.Case identification and line listing
Case finding according to case definition
Collect data on case patients
Arrange data into line listing

12. What to include in a line listing
Components of case definition
Case name
Date of symptom onset
Demographic variables(age, occupation)
Relevant risk factors

13. Example of a line listing
Name
Age
Gender
Date and time of onset
Symptom1
Abdominal pain
Symptom2
Fever
Symptom3
Diarrhea
Adress
Group event
Outcome
Ahmad 23
male
8/9/2010
2 pm
yes no
Hospitalization
Fatima 15
female
7/9/2010
10 am
i.v fluids
Kamal 8
Omar 34
6/9/2010
ORS
Layla 37
7 pm
nothing

14. 6.Perform descriptive epidemiology
Characterize the cases by
Time: epidemic curve, when become ill
Place: spot map, where the infection
acquired, address
Person: who was infected, what cases have in common (tables)

15. Importance of descriptive epidemiology
Describe clinical features of the illness
Describe demographic characteristics of affected persons
Identify population at risk
Provide clues to etiology, and mode of transmission
Guide interventions

16. 7. Generate a hypothesis guided by: Literature review
Information from previous outbreaks
Nature of suspected pathogen
Interviews with case patients
Local health officials opinion

17. 8. Test hypotheses
Current hypotheses may give a clue to the source of the outbreak
Compare with known facts
Conduct further studies if required (retrospective cohort, case control)

18. Which study to conduct Retrospective cohort:
Done for well defined relatively small population, every one is included, calculate and compare attack rates (relative risk)
Case-control:
Done for larger population, controls selection is crucial, calculate odds ratio

19. 9. Implement control measures
Take control measures as early as possible in order to:
Eliminate the source
Interrupt transmission
Reduce susceptibility

20. 9. Implement control measures
Control measures are guided by the results of epidemiological investigation and sometimes environmental specimens
Control measures should be carefully implemented and justified especially if closure of restaurants and institutions is included

21. 10. Communicate findings
Communicate findings through dissemination of summary investigation and recommendations for control to the public and the press
Communication helps to:
Document your findings
Justify your recommendations and control measures
Protect against legal issues

22. THANK YOU Jordan FETP