1. Information for action: Principles of surveillance Integrated Disease Surveillance Programme (IDSP) district surveillance officers (DSO) course

2. 2 Preliminary questions to the group Were you already involved in surveillance? If yes, what difficulties did you face? What would you like to learn about surveillance?

3. 3 Outline of the session 1.Surveillance definition 2.Data collection 3.Data analysis 4.Use of surveillance information for action

4. 4 Definition of epidemiology Epidemiology is the study of the distribution and determinants of health-related events or states in population groups and the application of this study to the control of health problems (Last JM ed. Dictionary of Epidemiology, Oxford University Press, 1995) Surveillance

5. 5 Surveillance: A role of the public health system The systematic process of collection, transmission, analysis and feedback of public health data for decision making Surveillance Could you drive without looking at the traffic? Can you make public health decisions in the absence of data?

6. 6 Information collected by the surveillance system Who get the disease? How many get them? Where they get them? When they get them? Why they get them? What needs to be done as response? Surveillance

7. 7 A common vision of surveillance District State Ministry of Health Is this surveillance? or “case reporting”? Could we work any other way? Surveillance

8. 8 A dynamic vision of surveillance Collect and transmit data Analyze data Feedback information Make decisions All levels use information to make decisions Surveillance The private sector can treat patients but only the public sector can coordinate surveillance

9. 9 What is contained in the definition of public health surveillance? Systematic  Ongoing, routine process  Consistent, generates a baseline Data collection Transmission Analysis Feedback Decision making Surveillance

10. 10 What is contained in the definition of public health surveillance? Systematic Data collection  Cases defined precisely and counted consistently  Not ALL cases, just the SAME types of cases every day Transmission Analysis Feedback Decision making Surveillance

11. 11 What is contained in the definition of public health surveillance? Systematic Data collection Transmission  Regular data transmission  Ongoing communication methods  Data are looked at before they are passed on Analysis Feedback Decision making Surveillance

12. 12 What is contained in the definition of public health surveillance? Systematic Data collection Transmission Analysis  Raw data converted into information  Case counts become rates Feedback Decision making Surveillance Critical stage: This is where the numbers start to make sense

13. 13 What is contained in the definition of public health surveillance? Systematic Data collection Transmission Analysis Feedback  Contains structured information  Stimulates reporting Decision making Surveillance

14. 14 What is contained in the definition of public health surveillance? Systematic Data collection Transmission Analysis Feedback Decision making  Decision making justifies the investment  Use of information improves the data Surveillance

15. 15 Case definition: The keystone of surveillance Can you count if you do not know what you are supposed to count? Can you report if you don’t know what you are supposed to report? Different persons may define a disease differently:  Malaria = Fever (Health worker)  Malaria = Fever and splenomegaly (Doctor)  Malaria = Fever with positive slide (Laboratory) Harmonization of these different criteria is needed  The system does not need to be exact, true or perfect  The system just needs to be consistent every day Data collection

16. 16 Being clear about what a case definition is and is not YES A case is an event An event is something that happens to:  A person,  In a given place,  At a given time A case definition is a set of criteria that triggers reporting  NO A case is not a person Events cannot be considered if you lack:  Person characteristics  Location  Onset date A case definition is not a diagnosis that decides the treatment Data collection

17. 17 Analysis of surveillance data Count, Divide and Compare (CDC)  Count Define cases to know what you count  Divide Divide cases by the population denominator (The denominator must match the numerator)  Compare Compare rates across groups Time, place and person analysis CDC for TLP See cholera outbreak example of time, place and person analysis in the following slides

18. 18 0 5 10 15 20 25 30 35 40 45 468 1012141618202224262830 2468 10 April Date of Onset May No. of cases Chlorination of overhead-tank repair of pipeline leakages Attack rate: 4 per 1000; No deaths Cases of diarrhea by date of onset, Garulia, West Bengal, 2006 (n=298) TIME analysis = Epidemic curve

19. 19 Distribution of diarrhea cases by households, Garulia, West Bengal, India, 2006 Index case Household with 1 case Household with 2-3 cases Household with 4-5 cases Household with 6+ cases Water pipeline Road Overhead tank Leakage point PLACE analysis= Map CDC for TLP

20. 20 Attack rate of diarrhea by age and sex, Garulia, West Bengal, India, 2006 CharacteristicsNumber of cases Population, 2006 Attack rate per 1,000 Age0 - 4 518,0306.4 5 -14 6820,0663.4 15 - 24 3915,4932.5 25 - 34 4214,1073.0 35 - 44 4211,1913.8 45 + 5615,6373.6 GenderMale 15843,7163.6 Female 14040,8093.4 Total298 84,5253.5 PERSON analysis = Table CDC for TLP

21. 21 Conclusions of the analysis of surveillance data in this example There is an outbreak of diarrhoea  Rectal swabs confirmed the diagnosis cholera It affects a specific area supplied by a pipeline that leaked Age distribution is compatible with cholera Decision: Investigate the source, examine the pipeline CDC for TLP

22. 22 Usefulness of surveillance data Describe trends Detect outbreaks Identify risk factors Estimate burden Generate hypotheses during outbreaks Evaluate programmes Use See examples for each of these uses in the following slides (Note the action point for each piece of information)

23. 23 Malaria in Kurseong block, Darjeeling District, West Bengal, India, 2000-2004 20002001200220032004 Months Incidence of malaria per 10,000 Incidence of malaria Incidence of Pf malaria Assess trends Use Decision: Investigate recent increase of incidence

24. 24 Decision: Investigate the outbreak Detect outbreaks 0 1 2 3 4 5 2001 Nov2002 Nov2003 Nov Months Incidence (%) PHC Village Incidence of diarrhea in Parbatia and the rest of its Primary health Centre (PHC), Orissa, India, November 2001-3 Use

25. 25 1 2 3 4 5 7 6 Attack rates per 100,000 89% of cases are from circles 1-4 with high proportion of Muslim community <5 10-14 15-19 20-25 Diphtheria incidence in Hyderabad, Andhra Pradesh, 2003-6 Identify risk factors Use Decision: Assess coverage among Muslims

26. 26 Incidence of malaria by age and sex, Purulia, West Bengal, India, 2004 Estimate burden Use Decision: Large burden: Evaluate the programme

27. 27 Attack rate per 10,000 500+ 200-499 20-199 0-19 Pond Old well Forest River Decision: Investigate and cover the wells Raise hypotheses during outbreaks Use Malaria rates in Sukna, Darjeeling, West Bengal, India, 2005

28. 28 Reported Yaws cases, India, 1996-2007 (June) Decision: Engage certification Evaluate the impact of programmes Use 0 500 1000 1500 2000 2500 3000 3500 4000 19961997199819992000200120022003200420052006 June '07 Year Number of cases

29. 29 Take home messages Surveillance is a lively line of communication that works both way  From bottom to top and from top to bottom A surveillance system counts the same events, consistently, every day Count, divide and compare to generate information on time, place and person  CDC for TPP Surveillance guides decisions

30. 30 Practical organization of this course Didactic sessions  Lectures  Case study Field exercise  Surveillance data analysis Field assignment  As you will go back to your district, we ask you to analyze surveillance data and send a short report to the institution