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

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? The usual warming up questions for a few minutes. 2

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

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 The difference between endemic and epidemic. Self explanatory. 4 Outbreaks

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) The difference between outbreak and epidemic. The take home message is: There is no formal difference. You are the one who decide how much importance you want to give to the event. If you are having lots of measles and none wants to help, call it a major epidemic. If it is a cluster well under controlled that the press is blowing out of proportion, call it a small outbreak. 5 Outbreaks

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 This slide is a booster dose for the lecture on alert. 6 Detection

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 The early warning signals for an outbreak. Provide additional examples. 7 Detection

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 The First Information Report is a quick document, a sort of post card from the field that says: This is the alert, we are on our way, we will investigate and we will bring more information. 8 Detection

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 Self explanatory. 9 Detection

Objectives of an outbreak investigation 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 Verify Recognize the magnitude Diagnose the agent Identify the source and mode of transmission Formulate prevention and control measures An outbreak comes from a break in the balance between the host, the environment and the agent. We need to understand this breach of balance to propose effective control measures. Hence the objectives of the investigations. 10 Investigations

The balance between investigation and control while responding to an outbreak Source / transmission Known Unknown Etiology Control +++ Investigate + Control + Investigate +++ This is an important slide. There is a balance between investigation and control measures in outbreak response. Underline the 2 x 2 table matrix that is the way we think in epidemiology ;-) 11 Investigations

Steps in outbreak response Verifying the outbreak Sending the rapid response team Monitoring the situation Declaring the outbreak over Reviewing the final report The steps in outbreak response. Response is a broader term that covers (1) investigations and (2) control measures. 12 Investigations

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 The step 1 of the outbreak investigation. We need to verify not to fall in the trap of pseudo outbreaks. 13 Investigations

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 Step 2. The rapid response team is the strong arm of outbreak response. Multi-disciplinary is the key word. The slide also introduces the key notion of the two levels: Generating hypotheses on the basis of descriptive information Testing hypotheses on the basis of analytical methods. We want people to be proficient at the first and aware of the second. 14 Investigations

Investigating an outbreak A flow chart presentation of the same. If the descriptive epidemiology suggests you are dealing with a very well known classical scenario, you may not need analytical methods. But if there is something you do not understand, then you do need them. 15

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 The following few slides will go through an example of hypothesis generation and testing. It is an hepatitis E outbreak in Orissa. 16

Strike among municipal 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 This is the TIME information: What does it suggest? Give a moment to the participants. Encourage them to follow the (1) describe and (2) analyze/ interpret steps. Probably a point source outbreak. It leads us to look into what happened one month earlier: There was a strike in the municipal water treatment plant. 15 10 5 3/1/04 1/1/04 1/3/04 1/5/04 1/7/04 1/9/04 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 2/2/04 2/4/04 2/6/04 2/8/04 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 3/3/04 3/5/04 3/7/04 17 Investigations

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 Underground water supply Pump from river bed 0 - 0.9 / 1000 1 - 9.9 / 1000 10 -19.9 / 1000 20+ / 1000 Chipat river This is the PLACE information. Give a moment to the participants. Encourage them to follow the (1) describe and (2) analyze/ interpret steps. It seems the disease clusters around the one source of water supply that comes directly from the river. 18 Investigations

Person: Attack rate compatible with HEV Attack rate of acute hepatitis (E) by age and sex, Baripada, Orissa, India, 2004 Cases Population Attack rate per 1000 Age 0-4 1 1012 0.1 5-9 11 21802 2 10-14 37 74004 5 15-44 416 51358 81 45+ 73 56153 13 Sex Male 341 102683 3.3 Female 197 101646 1.9 This is the PERSON information. Give a moment to the participants. Encourage them to follow the (1) describe and (2) analyze/ interpret steps. The attack rate by age and sex is highly compatible with HEV. 19 Investigations

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 Here we summarize the time, place and person information to “connect the dots” and come with a picture that generates an hypothesis: The hypothesis reads as: The river water may have been supplied untreated in the area of the outbreak because of the strike at the water treatment plant The river water may have been supplied untreated in the area of the outbreak because of the strike at the water treatment plant 20

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? Again we emphasize the difference between the two levels: Descriptive / hypothesis raising Analytical / hypothesis testing We want them to be proficient at the first and aware of the second. Brainstorm with the participants how to go about the analytical approach. 21 Investigations

Requires assistance from qualified field epidemiologist (FETP) 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) If we go for a fully fledged investigation with analytical methods, we will use the classical 10 steps. But that is beyond the skills we expect from the participants of the course. We would need help from a 2-year scholars of a Field Epidemiology Training Programme. 22

Consumption of pipeline water among acute hepatitis (E) cases and controls, Baripada, Orissa, India, 2004 Acute hepatitis Control Total Drunk water from river bed pump 493 134 627 Did not drink pump water 45 404 449 538 1076 92% of cases (493/538) drunk water from suspected source versus 25% (134/538) of controls If we get back to the Baripada HEV example, this is how the analytical epidemiology was approached with a case control study. See the language in purple at the bottom: The objective is to remain at a broad, conceptual level. 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

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 Back to our steps in the investigations. Now step 3: Monitoring the situation. 24 Investigations

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 And step 4. 25 Investigations

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 … and step 5. 26 Investigations

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) But we do not wait for an outbreak to happen. We want to be prepared. Here is a list of the actions to undertake to be ready. 27 Management

Managerial aspects of outbreak response Logistics Human resources Medicines Equipment and supplies Vehicle and mobility Communication channels Information, education and communication Media Daily update So far we have gone through the logical, methodological , intellectual aspects of outbreak investigations. But there is a managerial aspect also. 28 Management

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 The control measures to undertake. They should be based on the results of the investigations. If the outbreak says it was the food handler of the village there is no point in chlorinating the well! 29 Management

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 The take home messages. 30

Additional reading CDC text book on principles of epidemiology Section 5 of operations manual Module 8 of training manual Here are the additional resources you can use. 31 Detection