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Detection of unusual events Integrated Disease Surveillance Programme (IDSP) district surveillance officers (DSO) course.

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Presentation on theme: "Detection of unusual events Integrated Disease Surveillance Programme (IDSP) district surveillance officers (DSO) course."— Presentation transcript:

1 Detection of unusual events Integrated Disease Surveillance Programme (IDSP) district surveillance officers (DSO) course

2 2 Preliminary questions to the group Have you ever detected an outbreak? If yes, what difficulties did you face? What would you like to learn about early outbreak detection?

3 3 Outline of the session 1.From denial to vigilance 2.Early warning signals 3.Triggers in the Indian Integrated Disease Surveillance Programme (IDSP)

4 4 Cases of cholera by date of onset, South 24 Parganas, West Bengal, India, May AprilMay Number of cases When to investigate? Here? Never?

5 5 Fighting denial When are outbreaks investigated in your district? When the first cases occur?  An indication of vigilance When there is a large cluster?  Shows reactivity When most cases have occurred?  The team only acts under pressure Never  Denotes denial

6 6 Reasons why public health professionals might deny outbreaks  No skills to investigate  Additional work  No intervention to offer  Press pressure  Fears of sanctions Fighting denial

7 7 Turn challenges into opportunity Investigation methods can be learned Investigations become easier with practice Data guides effective prevention measures Good investigations impress the press Leaders appreciate signs that the situation is under control (e.g., ongoing investigation) Fighting denial

8 8 Improving the outbreak detection situation The number one obstacle to fight is denial Once there is a willingness to address outbreaks, technical methods may be used to ensure the earliest possible detection The system will not go from denial to early detection overnight  But every small progress matters It is never too late to investigate an outbreak  You will still learn, but it is more difficult

9 9 Two ways to detect unusual events Event-based surveillance  Reports of events Case-based surveillance  Routine surveillance data analysis Early warning

10 10 Components of early warning surveillance DataReports Alert Public health alert AnalyzeFilter ValidateVerify Assess Surveillance: Response Case-based surveillanceEvent-based surveillance Signal Post-outbreak strengthening Evaluate Investigate Control measures Early warning

11 11 Two ways to detect unusual events Event based surveillance  Collect reports (e.g., toll free line, internet search, press scan)  Filter  Identify signals  Verify Case base surveillance Early warning

12 12 Early warning signals for event-based surveillance Clustering of cases or deaths Single case of disease of epidemic potential Acute febrile illness of unknown etiology Two or more linked cases of meningitis, measles Unusual isolate Shifting in age distribution of cases High vector density Natural disasters Early warning

13 13 Sources of information for event-based surveillance Rumour register in each institution  Standardized format  Investigation for each entry  Tracking system to document follow up Community informants  Private and public sector Media  Important source of information, not to neglect 24 x 7 call centre Early warning

14 14 Two ways to detect unusual events Event based surveillance Case base surveillance  Collect data  Analyze data  Detect signals  Validate signals Early warning

15 15 Challenges to surveillance data analysis to detect unusual events Imperfect data  Changes over time  Multiple sources of information  Problem of quality and completeness Need an in-depth knowledge of the system  Evaluation  To know what is unusual, you need to know what is usual Early warning

16 16 Sources of false alarm Changes in the numerator  Increased awareness about a disease  Appointment of a new surveillance person  Acute reporting of old, chronic, cases Changes in the denominator  Population movements Early warning

17 17 Triggers in the context of the Indian Integrated Disease Surveillance Programme (IDSP) Threshold for diseases under surveillance that trigger pre-determined actions at various levels Based upon the number of cases in weekly report Trigger levels depend on:  Type of disease  Case fatality (Death / case ratio)  Number of evolving cases  Usual trend in the region Triggers

18 18 Levels of response to different triggers TriggerSignificanceLevels of response 1Suspected /limited outbreak Local response by health worker and medical officer 2Outbreak Local and district response by district surveillance officer and rapid response team 3Confirmed outbreak Local, district and state 4Wide spread epidemic State level response 5Disaster response Local, district, state and centre Triggers

19 19 * State may set their own triggers Malaria triggers Trigger 1  Single case of smear positive in an area where malaria was not present for a minimum of three months  Slide positivity rate doubling over last three months  Single death from clinically /microscopically proven malaria  Single falciparum case of indigenous origin in a free region Trigger 2:  Two fold rise in malaria in the region over last 3 months  More than five cases of falciparum of indigenous origin Triggers

20 20 Cholera triggers Trigger 1  A single case of cholera / epidemiologically linked cases of diarrhea  A case of severe dehydration / death due to diarrhea in a patient of >5 years of age  Clustering of cases in a particular village / urban ward where more than 10 houses have at least one case of loose stools irrespective of age per 1000 population Trigger 2  More than 20 cases of diarrhea in a village/geographical area of 1000 population Triggers

21 21 Typhoid fever triggers Trigger 1  More than 30 cases in a week from the entire primary health centre area  5 or more cases per week from one sub-centre of 5,000 population  More than 2 cases from a single village/urban ward/1000 population  Clustering of cases of fever Trigger 2  More than 60 cases from a primary health centre or more than 10 cases from a sub-center Triggers

22 22 Polio trigger One single case Triggers

23 23 Plague triggers Trigger 1  Rat fall Trigger 2  At least 1 probable case of plague in community Triggers

24 24 Japanese encephalitis triggers Trigger 1  Clustering of two or more similar case from a locality in one week Trigger 2  More than four cases from a PHC (30,000 population) in one week Triggers

25 25 Dengue triggers Trigger 1  Clustering of two similar case of probable Dengue fever in a village  Single case of Dengue hemorrhagic fever Trigger 2  More than four cases of Dengue fever in a village with population of about 1000 Triggers

26 26 Triggers for syndromic surveillance Fever  More than 2 similar case in the village (1000 Population) Diarrhea  See cholera Acute flaccid paralysis  1 case Jaundice  More than two cases of jaundice in different houses irrespective of age in a village or 1000 population Triggers

27 27 Basic responses to triggers There are triggers for each condition under surveillance Various trigger levels may lead to local or broader response Tables in the operation manual propose standardized actions to take following various triggers Investigations are needed in addition to standardized actions Triggers

28 28 Progressive response Levels of alert are progressively increasing Unusual signals require filtering / validation The best chance of detection is to:  Analyze regularly  Be familiar with the time, place and person characteristics of the diseases in your area Triggers

29 29 Public health events of international concern need to be reported as per new International Health Regulations (IHRs) Public health events  Sudden serious and unexpected event that require immediate action Outbreak of epidemic prone diseases Any other event that may have impact on the health of a community (natural or man-made catastrophes) International concern  Risk of spread beyond the borders of the affected country (agent/host/environment or capacity to contain the event) Triggers

30 30 Take home messages 1.Fight denial by showing what can be usefully done about outbreaks  Investigations  Control measures based on evidence 2.Consider case-based and event-based surveillance 3.Recognize triggers and respond to them as per guidelines

31 31 Additional reading Section 4 of IDSP operations manual Module 8 of training manual Triggers


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