Outbreak investigation ppt

PPT on Outbreak Investigations

1. Introduction to Investigating an Outbreak: The 13 Steps Approach J Sheriff Muideen (MBBS, MPH, FRSPH) 10/06/2021

2. Learning Objectives Know the Epidemiological concept of a disease Outbreak Know the Importance of Outbreak Investigation to Public Health Understand the 13 steps involved in an Outbreak Investigation Give and example of a Single Overriding Communication Objective (SOCO) in an Outbreak Investigation

3. Introduction to Investigating an Outbreak Introduction : The terms Cas e , Outbrea k , Epidemic , and Pandemic have become part of the world general vocabulary They can be use in Health , Financial, Marriage or other social maladies.

4. Introduction to Investigating an Outbreak Introduction: Imagine comments like: An Epidemic of Obesity among our Children An Outbreak of Corporate Corruption A case of Failed Marriage A Pandemic Religion Phobia

5. Introduction to Investigating an Outbreak The word “ Outbreak ’ gets our attention and indicates that something is awry But what is an Outbreak from Epidemiologic Point of view? How do we determine if an event or Observation represent an Outbreak ?

6. Introduction to Investigating an Outbreak An  outbreak  is a sudden occurrence of a disease in a community, which has never experienced the disease before or when cases of that disease occur in numbers greater than expected in a  defined   area.

7. Level of Disease in Epidemiology Level of Disease in Epidemiology Case definition : A case definition is a set of standard criteria for determining whether an individual should be categorized (based on presentation, clinical features and/or signs and symptoms) as having a particular disease or health-related condition.

8. Level of Disease in Epidemiology Sporadic : refers to a disease that occurs infrequently and irregularly Cluster :   several new cases seen in a particular area during a relatively brief period of time Outbreak :  carries the same definition of epidemic, but is often used for a more limited geographic area

9. Level of Disease in Epidemiology Epidemic  refers to an increase, often sudden, in the number of cases of a disease above what is normally expected in that population in that area   Endemic  refers to the constant presence and/or usual prevalence of a disease or infectious agent in a population within a geographic area Pandemic  refers to an epidemic that has spread over several countries or continents, usually affecting a large number of people

10. Introduction to Investigating an Outbreak Epidemiological Concept of a disease Outbreak Knowing what an outbreak is, is crucial and essential in public health. Timely Identification of an outbreak will not only reduce its negative impact, but also, save cost .

11. Reasons to Investigate an Outbreak Identify the source of the outbreak control and Prevention measures Strengthen existing/Develop new strategies to prevent future occurrence of outbreak Training and Research Opportunities Address public concern Because it’s your Job…..

12. How do we Detect an Outbreak Sources of an Outbreak Information From surveillance Data Medical Practitioner/Pharmacy stores From Affected Persons/Groups Public Concerns From Media

13. When To Investigate an Outbreak Always Consider the following Factors: Severity of the disease Transmissibility of the disease Ongoing Illness or Exposure of the disease Growing Public Concern Unanswered Questions

14. Principle of Outbreak Investigation Be systematic in your approach Follow the same step for every type of outbreak Write Down Case Definition Ask same questions from all cases

15. Principle of Outbreak Investigation Stop Often to re-assess what you know Line list and epi curve provide valuable information; many investigations never go past this point. Line List: Name/Identifier Age Gender Nationality Place of work Residence Date of Onset Date of Notification Occupation Diagnosis Reporting facility Status Action

16. Principle of Outbreak Investigation Epi Curve : Epidemic or epidemiological curve is a statistical chart showing the onset and time distribution of epidemic cases

17. Principle of Outbreak Investigation

18. Principle of Outbreak Investigation Coordinate with partners and stakeholders e.g. Environmental and Epidemiologist as well as households and healthcare workers.

19. The 13 steps of an outbreak Investigation Identify investigation team, resources needed and prepare for field work Establish the existence of an Outbreak Verify the Diagnosis Define and Identify cases Find Cases systematically and develop line listing Perform Descriptive Epidemiology (Orientate your data in term of Time, Place & Person) Develop your Hypotheses (i.e. explain the exposure that cause the disease)

20. The 13 steps of an outbreak Investigation 8) Evaluate your Hypotheses epidemiologically (Determine who is at risk of becoming ill) 9) Reconsider, refine, and re-evaluate hypotheses as necessary 10) Execute additional studies (compare and reconcile with laboratory or environmental studies) 11) Implement Control and Prevention Measure 12) Initiate or maintain surveillance 13) Communicate your findings with follow up recommendations

21. Steps of an Outbreak Investigation Step 1: Identify investigation team, resources needed and prepare for field work Investigation Resources Epi Team with scientific knowledge Supplies Equipment Administration Administrative procedure (cash advances, travel documents) personal matters Consultation Know expected role Local Contact Person

22. Steps of an Outbreak Investigation Step 2 : Establish the existence of an Outbreak Compare the current number of cases with the number of cases from comparable period during the previous years. surveillance records hospital records, registries, mortality statistics, data from neighbouring areas or community survey

23. Steps of an Outbreak Investigation Step 3: Verifying the Diagnosis Ensure proper diagnosis of reported cases Rule out laboratory error as the basis for the increase in diagnosed cases review clinical findings review laboratory results summarize the clinical findings with frequency distribution visit patients

24. Steps of an Outbreak Investigation Step 4: Define and Identify cases A) Establish a case Definition standard set of criteria for the health condition clinical criteria (signs and symptoms) restrictions by time, place and person apply without bias NOTE: Never include the EXPOSURE or RISK FACTOR in the case definition

25. Steps of an Outbreak Investigation Examples of case definition of diseases used by the National Epidemic Sentinel Surveillance System (NESSS ). Tuberculosis: Fever, Cough >3 weeks, weight loss, Night sweating, Significant CXR findings, Positive Monteux, Positive AAFB sample (3 series). Component of Case Definition Person …………. Type of Illness (e.g. a person with TB) Place …………... Location of Suspected Exposure Time …………… Based on incubation period (if known)

26. Steps of an Outbreak Investigation Step 4: Define and Identify Cases B) Identify and Count Cases Identifying information ( name, address, telephone no) demographic information (age, sex, race, occupation) clinical information (date of onset, hospitalization, death Risk factor information ( food or water sources, toilet facility Reporter information

27. Steps of an Outbreak Investigation Step 5: Find Cases systematically and develop line listing What to Put on a Line List 1. Clinical information • Symptoms (type, duration) • Onset dates and/or times 2. Demographic information 3. Exposure information Use line list to summarize information

28. Steps of an Outbreak Investigation Step 6: Perform Descriptive Epidemiology (Orientate your data in terms of Time, Place & Person) characterize by TIME . Draw an epidemic curve can be used to determine: • the type of epidemic • the difference between maximum & minimum incubation period • the probable time of exposure • the incubation period when probable time of exposure is known

29. Steps of an Outbreak Investigation Step 6: Perform Descriptive Epidemiology characterize by PLACE geographic extent spot map area map

30. Steps of an Outbreak Investigation Step 6: Perform Descriptive Epidemiology characterize by PERSON host characteristics age sex race medical status exposures occupation leisure activities tobacco use use of medications/drugs

31. Steps of an Outbreak Investigation Step7: Develop your Hypotheses (i.e. explain the exposure that cause the disease) Consider: source of the agent mode of transmission vectors of transmission risk factors * hypotheses should be tested.

32. Steps of an Outbreak Investigation Step 8: Evaluate your Hypotheses epidemiologically (Determine who is at risk of becoming ill) • compare with established facts • use analytical epidemiology case-control studies retrospective cohort studies

33. Steps of an Outbreak Investigation Step 9: Reconsider, refine, and re-evaluate hypotheses as necessary why: 1) unrevealing analytic studies - poor hypotheses 2) need more specific exposure histories 3) need more specific control group

34. Steps of an Outbreak Investigation Step 10: Execute additional studies (compare and reconcile with laboratory or environmental studies Additional Studies • Types Cohort Case-control • Designed to assess exposures equally among ill and non-ill

35. Steps of an Outbreak Investigation Step 10: Cohort Studies Include EVERYONE who could have been exposed – Only use if a complete list is available Meeting attendees, students, LTCF (Long-Term Care Facility) residents, etc. Measure of association = Relative Risk Relative Risk (RR ) RR = 1.0, Risk same among exposed and unexposed RR > 1.0, Risk is HIGHER among exposed RR < 1.0, Risk is LOWER among exposed Case-Control Studies

36. Steps of an Outbreak Investigation Step 10: Case-Control Studies Compare exposures among ill persons (case-patients) and non-ill persons (controls) Used when a complete list is not available or too large – Restaurant outbreaks, national outbreaks, etc. Measure of association = Odds Ratio Interpretation of Odds Ratio OR = 1.0 Same odds of exposure among ill and non-ill OR > 1.0 HIGHER odds of exposure among ill OR < 1.0 LOWER odds of exposure among ill

37. Steps of an Outbreak Investigation Step 11 : Implement Control and Prevention Measure For Primary public health reason • prevent additional cases • prevent outbreaks in the future

38. Steps of an Outbreak Investigation Control Measures Can occur at any point during outbreak Isolation, cohorting, product recall Balance between preventing further disease and protecting credibility and reputation of institution Should be guided by epidemiologic results in conjunction with environmental investigation

39. Steps of an Outbreak Investigation Step 12: Initiate or maintain surveillance Once control and prevention measures have been implemented, they must continue to be monitored. I nitiate or continue active surveillance to: …1) continue to monitor the situation and determine whether the prevention and control measures are working …2)  Is the number of new cases slowing down or, better yet, stopping? Or are new cases continuing to occur?

40. Steps of an Outbreak Investigation Step 13: Communicate your findings with follow up recommendations Summarize the Investigation, Its finding and Outcome in a report Communicate the report to the appropriate authorities and/or organizations Through: 1) Writing and disseminating full reports 2) Meetings and discussions

41. Steps of an Outbreak Investigation • local and mass media. To the : • local government officials • local health workers • concerned authorities • regional health authorities • Department of Health Finally, a report that finds its way into the public health literature serves the broader purpose of contributing to the knowledge base of epidemiology and public health

42. Steps of an Outbreak Investigation Step13 : Follow-up Recommendation is based on: what activities have been undertaken if health status has improved if health problems has been reduced

43. Steps of an Outbreak Investigation Conclusion Epidemiologic investigations are essential to determine source of outbreaks Be systematic Follow the steps accordingly.

44. Steps of an Outbreak Investigation

45. Questions…..Q#1 For the month of August, 12 new cases of tuberculosis and 12 new cases of West Nile virus infection were reported to a district PMD. You are not sure if either group of cases is a cluster or an outbreak. What additional information might be helpful in making this determination?

46. Answer… First, you should check the dates of onset rather than dates of report… Classifying the cases as an outbreak depends on whether the 12 cases exceed the usual number of cases reported in August in that District . The number of cases during August could be compared with: a) the numbers reported during the preceding several months; and b) the numbers reported during August of the preceding few years.

47. Q#2 Which of the following is not a reason to investigate an outbreak? For training and research purpose To Identify source of disease outbreak For Control and Prevention measure Compare exposures among ill persons and non-ill persons Address public concern

48. Q#3 All are sources of outbreaks information except From surveillance Data Medical Practitioner/Pharmacy stores From Affected Persons/Groups Passers-by and researchers From Media

49. Q#4 For each of the following situations, identify whether it reflects: Sporadic disease Endemic disease Hyperendemic disease Pandemic disease Epidemic disease ____ 22 cases of legionellosis occurred within 3 weeks among residents of a particular neighborhood (usually 0 or 1 per year) ____ Average annual incidence was 364 cases of pulmonary tuberculosis per 100,000 population in one area, compared with national average of 134 cases per 100,000 population ____ Over 20 million people worldwide died from influenza in 1918–1919 ____ Single case of histoplasmosis was diagnosed in a community ____ About 60 cases of gonorrhea are usually reported in this region per week, slightly less than the national average

50. Q#5 Factors that influence a health department’s decision whether or not to conduct a field investigation in response to one or more cases of disease include: The nature of the disease The number of cases Resources available None of the above All of the Above

51. Q#6 A case definition during an outbreak investigation should specify: Clinical features Time Place Person Hypothesized exposure

52. References Center for Disease Prevention and Control (213). Principles of Epidemiology in Public Health Practice, Third Edition An Introduction to Applied Epidemiology and Biostatistics . 3 rd Ed. Pan American Health Organizations (2018). Steps in outbreak Investigations https://cursos.campusvirtualsp.org/mod/tab/view.php?id=34164&forceview=1 Introduction to Outbreak Investigation . http://samples.jbpub.com/9780763784591/84591_CH02_FINAL.pdf