Outbreak investigation, response and control

1. Outbreak investigation, response and control Integrated Disease Surveillance Programme (IDSP) district surveillance officers (DSO) course

2. Preliminary questions to the group • What is your experience in outbreak investigations? • If yes, what difficulties did you face? • What would you like to learn about outbreak investigations? 2

3. Outline of the session • Outbreaks and epidemics • Outbreak detection • Outbreak investigation • Managerial aspects of outbreak investigations 3

4. Endemic versus epidemic • Endemicity • Disease occurring in a population regularly at a usual level • Tuberculosis, Malaria • Epidemics • Unusual occurrence of the disease in excess of its normal expectation • In a geographical location • At a given point of time • e.g. Hepatitis E, measles, cholera 4 Outbreaks

5. Outbreaks versus epidemics • Occurrence of cases of an illness in excess of expected numbers • Scale • Outbreak • Limited to a small area, within one district or few blocks • Epidemic • Covers larger geographic areas • Linked to control measures in district/state • No exact precise threshold: Use a word or the other according to whether you want to generate or deflect attention • Be aware of legal implications of the use of the term “Epidemic” in India (Epidemic disease act, being revised) 5 Outbreaks

6. Sources of information to detect outbreaks • Event-based surveillance • Rumour register • To be kept in standardized format in each institution • Rumours need to be investigated • Community informants • Private and public sector • Media • Important source of information, not to neglect • Case-based surveillance • Review of routine surveillance data and triggers 6 Detection

7. Early warning signals for an outbreak • Clustering of cases or deaths • Increases in cases or deaths • Single case of disease of epidemic potential • Acute febrile illness of an unknown etiology • Two or more linked cases of disease with outbreak potential • (e.g., Measles, Cholera, Dengue, Japanese encephalitis or plague) • Unusual isolate (Cholera O 139) • Shifting in age distribution of cases (Cholera O 139) • High vector density • Natural disasters 7 Detection

8. Importance of timely action: The first information report (Form C) • Filled by the reporting unit • Submitted to the District Surveillance Officer as soon as the suspected outbreak is verified • Sent by the fastest route of information available • Telephone • Fax • E-mail 8 Detection

9. The rapid response team • Composition • Epidemiologist, clinician and microbiologist • Entomologist when vector-borne disease • Gathered on ad hoc basis when needed • Role • Confirm and investigate outbreaks • Responsibility • Assist in the investigation and response • Primary responsibility rests with local health staff 9 Detection

10. Verify Recognize the magnitude Diagnose the agent Identify the source and mode of transmission Formulate prevention and control measures Host Environment Agent An outbreak comes from a change in the way the host, the environment and the agent interact: This interaction needs to be understood to propose recommendations Objectives of an outbreak investigation 10 Investigations

11. The balance between investigation and control while responding to an outbreak 11 Investigations

12. Steps in outbreak response • Verifying the outbreak • Sending the rapid response team • Monitoring the situation • Declaring the outbreak over • Reviewing the final report 12 Investigations

13. Step 1: Verifying the outbreak • Validate the source of information • Change in the reporting system • Change in the population size • Acute reporting of old, chronic cases • Check with the concerned medical officer: • Abnormal increase in the number of cases • Clustering of cases • Epidemiological link between cases • Triggering event • Deaths 13 Investigations

14. Step 2: Sending the rapid response team • Review if the source and mode of transmission are known • If not, constitute team with: • Medical officer • Epidemiologist • Laboratory specialist • Formulation of hypothesis on basis of the description by time, place and person (Descriptive epidemiology) • Does the hypothesis fits the fact • YES: Propose control measures • NO: Conduct analytical studies 14 Investigations

15. Investigating an outbreak 15

16. Example: Outbreak of acute hepatitis (E) in Baripada, Orissa, 2003 • Identification of a cluster of acute hepatitis cases • Diagnosis: HEV infection • Use time, place and person analysis of surveillance data to suggests hypotheses 16

17. Time: A cluster a month after a strike in the water treatment centre Cases of acute hepatitis (E) by date of onset, Baripada, January-March 2004 Investigation 45 started Cases 40 Deaths 35 Strike among municipal Workers: Water treatment stopped 30 25 Number of cases and deaths 20 15 10 5 0 3/1/04 1/1/04 1/3/04 1/5/04 1/7/04 1/9/04 2/2/04 2/4/04 2/6/04 2/8/04 3/3/04 3/5/04 3/7/04 1/11/04 1/13/04 1/15/04 1/17/04 1/19/04 1/21/04 1/23/04 1/25/04 1/27/04 1/29/04 1/31/04 2/10/04 2/12/04 2/14/04 2/16/04 2/18/04 2/20/04 2/22/04 2/24/04 2/26/04 2/28/04 17 Investigations

18. Underground water supply Pump from river bed Place: Highest rates next to the pump taking water from river bed Attack rate of acute hepatitis (E) by residence, Baripada, Orissa, India, 2004 Attack rate 0 - 0.9 / 1000 1 - 9.9 / 1000 10 -19.9 / 1000 20+ / 1000 Chipat river 18 Investigations

19. Person: Attack rate compatible with HEV Attack rate of acute hepatitis (E) by age and sex, Baripada, Orissa, India, 2004 19 Investigations

20. What hypotheses would you generate for the outbreak of acute hepatitis (E) in Baripada, Orissa, 2003? • Time: • It happens a month after a strike in the water treatment plant • Place: • It is clustered around a water source that takes water from the river • Person: • Adults are mostly affected The river water may have been supplied untreated in the area of the outbreak because of the strike at the water treatment plant 20

21. Descriptive versus analytical investigations • Descriptive investigations • Based upon cases only • Look at time, place and person epidemiology • Raise hypotheses • Analytical investigations • Based upon a study of the cases and non-cases • Compare: • Cases with controls with respect to exposure • Exposed with unexposed with respect to incidence • Test hypotheses • How could we test the hypothesis for the Baripada investigation? 21 Investigations

22. Steps of a full outbreak investigation using analytical epidemiology to identify the source of infection • Determine the existence of an outbreak • Confirm the diagnosis • Define a case • Search for cases • Generate hypotheses using descriptive findings • Test hypotheses based upon an analytical study • Draw conclusions • Compare the hypothesis with established facts • Communicate findings • Execute prevention measures Requires assistance from qualified field epidemiologist (FETP) 22

23. Consumption of pipeline water among acute hepatitis (E) cases and controls, Baripada, Orissa, India, 2004 92% of cases (493/538) drunk water from suspected source versus 25% (134/538) of controls Analytical epidemiology compares cases and non cases or exposed versus unexposed to test the hypothesis generated on the basis of the time, place and person description 23 Investigations

24. 3. Monitoring the situation • Trends in cases and deaths • Implementation of containment measures • Stocks of vaccines and drugs • Logistics • Communication • Vehicles • Community involvement • Media response 24 Investigations

25. 4. Declaring the outbreak over • Role of the district surveillance officer / Medical health officer • Criteria • No new case during two incubation periods since onset of last case • Implies careful case search to make sure no case are missed 25 Investigations

26. 5. Review of the final report • Sent by medical officer of the primary health centre to the district surveillance officer / medical and health officer within 10 days of the outbreak being declared over • Review by the technical committee • Identification of system failures • Longer term recommendations 26 Investigations

27. Outbreak preparedness: A summary of preparatory action • Formation of rapid response team • Training of the rapid response team • Regular review of the data • Identification of ‘outbreak seasons’ • Identification of ‘outbreak regions’ • Provision of necessary drugs and materials • Identification and strengthening appropriate laboratories • Designation of vehicles for outbreak investigation • Establishment of communication channels in working conditions (e.g., Telephone) 27 Management

28. Managerial aspects of outbreak response • Logistics • Human resources • Medicines • Equipment and supplies • Vehicle and mobility • Communication channels • Information, education and communication • Media • Daily update 28 Management

29. Control measures for an outbreak • General measures • Till source and route of transmission identified • Specific measures, based upon the results of the investigation • Agent • Removing the source • Environment • Interrupting transmission • Host • Protection (e.g., immunization) • Case management 29 Management

30. Take home messages • Do not ignore or hide outbreaks • Respond to early warning signals • Investigate outbreaks to: • Control the current outbreak • Learn about the disease in the local setting • Outbreaks require an organized, well managed response 30

31. Additional reading • CDC text book on principles of epidemiology • Section 5 of operations manual • Module 8 of training manual 31 Detection