outbreak of an epidemic.outbreak of an epidemic ppt

About outbreak of an epidemic

1. OUTBREAK INVESTIGATIONS

2. INTRODUCTION Outbreak -occurrence of a disease at a rate greater than that expected within a specific geographical area and over a defined period of time Cluster – aggregation of cases in a given area over a particular period without regard to whether no.of cases is more than expected.

3. DEFINITION Outbreak/epidemic - 2 or more linked cases of same illness or Observed number of cases exceeds the expected number or A single case of rare disease caused by a significant pathogen

4. PSEUDO-OUTBREAK Real clustering of false infections or artifactual clustering of real infections Occur when an increased no of positive tests without presence of true outbreak Reasons Lab factors (50%)- new test, new tech, normal flora /contaminant interpreted as pathogen Surveillance factor- introduction of newer method / change in HAI definition Ward level- incorrect diagnosis, mislabeled specimen, contamination during collection Environmental- contaminated tap water for endoscope cleaning Administrative factors- increased interest becoz of lpcal / national awareness

5. EPIDEMIC CURVE Graphical display (histogram) X axis- time (date of onset) Y axis- number of incident cases in an outbreak

6. of the epidemic over time eg :- Are there many cases / just a few? Source and pattern of spread in population(Point source, Continuous, Intermittent, propagated) TOE of cases to the source of infection still on upswing or downslope , or epidemic is already ended. This helps in predicting cases in near future cases that do not fit into the body of curve and lie on either side of the curve

7. OUTLIERS Provide imp clues- An early case(index case) may represent an unrelated case, a source of the epidemic, or a person who was exposed earlier than most of the cases Late cases may represent unrelated case with long IP , 2 cases or persons exposed later than most others

8. TYPES OF OUTBREAK Based on the type of epidemic curve Common source outbreak- 3 types Point source Continous common source Intermittent common source Propagated outbreak

9. COMMON SOURCE OUTBREAK Group of persons are exposed to an infectious agent or toxin from the same source (contaminated food, water supply) controlling the source stops the outbreak

10. POINT SOURCE OUBREAK Group of people are exposed to the same source over a brief time Everyone becomes ill within 1 IP Outbreak lasts for short duration Cases do not arise from person to person spread Eg :- grp of people with diarhoea due to shigellosis following a party

11. Bell shaped epidemic curve

12. Index case 1 st patient that indicates the existence of an outbreak(not 1 st case of outbreak) Index case in a point source outbreak may not be the primary case bt usually the case which has occurred few days earlier and has been either not noticed / not reported initally / has been discharged from hospital

13. CONTINOUS COMMON SOURCE Persons are exposed to same source bt exposure is prolonged over a period of days,wks /longer Outbreak persists for longer eg :- contaminated water supply that doesn’t get fixed Outbreaks begin abruptly, because many people exposed simultaneously No case rises beyond 1 IP following the termination of the exposure

14. Epidemic curve- flatten with peaks widened, reaaches a plateau that is sustained over time, until the source is removed

15. INTERMITTENT COMMON SOURCE Not well controlled Exposure occurs intermittently Outbreak tend to recur Could be seasonal / weather related / common source ( industrial contaminant being emitted at intervals)

16. irregularly jagged curve with unevenly spaced peaks reflecting the intermittent nature of exposure

17. PROPAGATED OUTBREAK No common source Spreads from person to person Can last longer Outbreak begins from an index case then develops into epidemic Epidemic continues until susceptible individuals decline / intervention measures take effect

18. progressively taller peaks

19. OUTBREAK INVESTIGATION General outbreak control guideline in hospital Reviewed periodically Updated every 1-2 yrs/ when required

20. STEPS prepare for field work Recognize the outbreak and prepare to investigate Verify the diagnosis & confirm that an outbreak exists Construct a working case definiton Find cases systematically & record information Perform descriptive epidemiology with respect to time , place and person Develop hypothesis Evaluate hypothesis epidemiologically Reconsider,refine,and re-evaluate hypothesis Compare & recocile with laboratory and environmental studies Implement infection control measures initiate or maintain surveillance Communicate findings

21. 1.Prepare For Field Work Not always the 1 st step public health officials ( investigarors )conduct a field investigation only if they cannot reach a convincing conclusion If no of cases increases - They collect information to perform descriptive epidemiology without leaving their desks

22. 2.Recognize The Outbreak And Prepare To Investigate A,Establish the existance of an outbreak Find out the reliability of both clinical & laboratory information Compare with baseline data from HAI surveillance data to determine if cases are more than expected , compared to previous wks/ mon if 2 or more linked cases of same illness present Ruling out of psuedo outbreaks(new staff,new procedures,new tests,staff patient ratio) Differentiate btw outbreak and cluster If outbreak is not confirmed , inform the clinical team who have reported the outbreak

23. B,Immediate control measures If immediate infection control measures are needed, HCWs should be advised to -reinforce on std precautions -adhere to transmission based precautions for disease suspected

24. C,Notify and communicate HCWs ,HICC & administrators for control measures Laboratory for further testing for epidemiological typing Integrated disease surveillance program(IDSP)if it is a notifiable disease

25. D,Formation of outbreak control team Minor outbreaks in hospital – dealt by HICC alone Large/serious outbreaks/unusual microorganism- as per hospital policy , outbreak control team (OCT) should be convened OCT – multidisciplinary grp which work together to investigate an outbreak responsible for planning & cordinating the investigation members- administartor,treating clinician,HICC team, epidemiologist,microbiologist & public relation officer Team leader – team leader (one of the OCT members )- cordinates all the activity of the team & act as primary point of contact

26. Role of OCT Draws outbreak control plan (areas of individual responsibilities, action plans of all members) Implementation & monitor infection conctrol measures recommended by HICC Special cleaning & disinfection procedures Oversees communication to all relevant grps Facilitates medical care of pts Provide PPE / training in using PPE Set up special incident room to coordinate the outbreak If major incident- OCT should seek advice from experts at regional and national levels

27. Role of treating clinical team When outbreak is suspected , clinical team should Inform – all suspected outbreaks to HICC, microbiology lab , epidemiologist, & all members of OCT Isolate- all suspected cases asap Record- DOA, time of onset of symp . , clinical diagnosis. Relevant specimens – to laboratory after consultation with HICC & microbiologist Restrict movement- of staff, patients& visitors Implement- infection control measures Assist – in formulating a case definition Train – other physicians on treatment & prophylaxis guideline

28. Role of HICC Objectives of HICC – rapid recognition of outbreaks HICC must -ensure implementation of infection control measures (std & transmission based precautions) -organize educational/training sessions to HCWs -Monitor infection control practices(hand hygiene audit) -Assist epidemiologist for line listing the cases & establishing case definition -Arrange pre & PEP incl. staff vaccination -Assist clinical team in active surveillance for case finding

29. Role of microbiology laboratory Culture & AST – identify the organism to species level with AST Identifying a suspected outbreak-establishing epidemiological link btw outbreak isolates by matching their antibiogram pattern communicate to clinicians & help in initiating early investigation of outbreak Epidemiological typing- PFGE & sequencing to establish epidemiological link btw isolates Perform environmental surviellance (surface , air ,water) – to trace source Staff screening for MDRO - to determine source of infection

30. Role of epidemiologist Formulate a case definition , classify cases into suspect, probable, confirmed/ ruled out Maintain a current line listing of cases & construct epidemic curve Conduct active & enhanced surveillance, prospectively/ retrospectively for detecting missed cases. Maintain documentation of all information , report and notify to concerned authorities Ensures final written report is submitted within 30 days of end of outbreak

31. Role of administrator Ensure that sufficient resources are available to respond to outbreak & control its spread including PPE, drugs, vaccine, disinfectant, reimbursemnt to HCWs / OCT members for addl working hrs.

32. 3.Verify The Diagnosis & Confirm That An Outbreak Exists Verify the diagnosis is imp As control measures are disease specific To rule out laboratory error STEPS Review the clinical findings, lab results & request addl lab tests if necessary (epidemiological typing to confirm clonality ) Multidisciplinary team – visit pt & reelicit detailed clinical history Summarize clinical features using frequency distribution (useful in verifying diagnosis, developing case definition) Review the scientific literature

33. 4.Construct A Working Case Definition Std set of criteria for deciding whether an individual should be classified as having the disease under outbreak investigation Cases classified as Confirmed- laboratory verified Probable-typical clinical features Suspect-fewer typical clinical features

34. 5.Find Cases Systematically & Record Infomation A . Find cases Carried out by Active surveillance – history from suspected cases/contacts, onsite field visit Passive surveillance- via mail/telephone & asking for reports of similar cases Follow up- confirmed & discharged to know outcome Contact tracing-asking the pts (effective strategy of case finding)

35. b.Standard case report form Questionnaire /data abstraction form (form 14) Identifying information- contact detail to communicate later Demographic information-age, sex,occupation Clinical information- signs & symptoms Risk factor information- predisposing factors(possible exposure) Reporter information(treating physician/lab)- to seek addl information if req

36. C.Develop line listing of cases Line listing= compiling critical information from case report in an organized manner Comprises - spreadsheet with rows & columns Rows represent – cases Column – variables(demographic information, clinical details, exposure) Performed- manually / electronically

37. 6.Perform Descriptive Epidemiology descriptive epidemiology = process in which the outbreak is characterized by time, place, person Helps – etiology, source, mode of transmission Epidemic curve is used to characterize an outbreak with respect to time, displays time trend Assessment of outbreak by place – geographic extent , demonstrate cluster Spot map – simple. Useful technique – illustrate whether cases live,work Person related – charecteristics ( age,sex,medical status) & possible exposure ( occuption,medical history)

38. 7.Develop Hypothesis Hypothesis =Proposed explanation made on the basis of limited evidence about disease( agent,soiurce mode,RF )

39. 8.Evaluate Hypothesis Epidemiologically Evaluate probabilty of hypothesis - by performing epidemiological studies Retrospective cohort study – Study of choice for an outbreak in a small , well defined population(single ward) Tested by calculating the relative risk If RR > 1 = exposure is associated with disease Higher RR, more is the chance of association If RR <1 = exposure not associated with disease

40. Case control study For larger outbreak, when population is not well defined Investigator asks persons with disease and without disease about their exposures Investigator then calculates odds ratio(relation btw exposure & disease)

41. 9.Reconsider,refine & Revaluate Hypothesis Investigator – revisit , rephrase, refine hypothesis if needed Refined hypothesis tested again by appropriate epidemiological study

42. 10.Compare & Reconcile With Lab& Environmental Studies Help in verifying diagnosis Determining the source of outbreak

43. 11.Implement Infection Control Measures Std and transmission based precaution Check whether initial infection control measures were adequate Monitoring – hand hygiene audit, PPE audit, bundle care audit , BMW segregation audit Compare infection control implementation with control of outbreak- if control of outbreak is not achieved , look for alternate source of transmission & implement appropriate addl precautions.

44. 12.Initiate Or Maintain Surveillance Active surveillance to monitor the situation and remain alerts for similar situations in future

45. 13.Communicate Findings A.Communicate within hospital To relevant staff by the OCT Communication should consist of Appropriate signage to limit access to a room Electronic alerts on medical record to manage cases and contacts Provision of education and written materials to visitors Pts and pts relative must be kept informed by the clinical team

46. B.Final report Summarize – investigaion with findings , outcome Communicate this report in 2 forms Oral briefing for local authorities- by OCT Ivestigators describe what they did/ found/think should be done about it Should be able to defend their conclusion & recommendations

47. Written report introduction, background,methods,results , discussion and recommendations Serves as record of performance & document for potential legal issues As reference if health dept encounters similar situation in future

48. C. Lookback investigations Process of identifying, tracing,recalling , counseling and testing pts/ HCWs (exposed during outbreak) Eg - follow up of HCWs – needlestick injury, exposed to open TB

49. REFERENCE Essentials of hospital infection control

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