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Outbreak Management

E.McNamara

PHL,HSE,SWA. and St James’s Hosp.

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Outbreak definitions

Cluster - 2+ cases

- related in time/place

- may not be above expected

Outbreak - as cluster but

- exceeds expected number Epidemic - as outbreak

- but implies crisis.

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1 Preliminary assessment

Is it an outbreak? Confirm the diagnosis Is further investigation needed?

Epidemiological Environmental Microbiological

Any immediate control measures?

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Preliminary assessment - is it an outbreak?

Who identified problem? How many cases or deaths? Expected number of cases or deaths? What tests done and any results? Any change in clinical or lab practice? Any obvious link between cases?

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Preliminary assessment- confirm the diagnosis

Review clinical case histories Interview several cases Discuss tests/specimens with lab Arrange tests/get results quickly Repeat tests or confirmatory tests? Consult experts?

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Preliminary assessment - Is further investigation needed?

illness serious? Cases still occurring? More than 1 location involved? Any secondary cases? Risk of recurrence?

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Preliminary assessment - immediate control measures?

Prevent further cases: Stop symptomatic food handlers working? Close ward, Stop admissions? Clean/disinfect premises or equipment? Cease drinking water? Close premises/stop production? Review operational practices Recall product? Prevent person-to-person spread Offer prophylaxis e.g. immunisation

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Case definition and identification

Case ascertainment Case definition Define population at risk Quantification of incident.

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Case definition and identification:

Time Place Person Symptoms Lab results.

Confirmed Probable Possible

Master List

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Descriptive study:

Time, place and person Data collection

standard format

line listing

denominator data Data analysis

epidemic curve

attack rates

Generate Hypothesis.

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Analytical studies?To Test hypothesis

Cohort Study Start with population (cohort) exposed to factor Calculate relative risk (RR) of exposure.

Case-control study Start with cases Identify controls Calculate odds ratio (estimate of RR)

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Special studiesVerify hypothesis, Source.

Microbiological Identify Pathogen Typing of isolates Food and environmental samples?

Other Specialities Veterinary, Enviromental Meteorological data Tracer studies e.g. water, air Entomological

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Control Measures

Remove sourceIsolate/treat case

Destroy/treat food or other source Protect persons at risk

Hygiene/prophylaxis Prevent recurrence

Make recommendations

Produce guidelines/change law

Audit interventions

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Communication

During the investigation Information for public and professionals

At the end of the investigation

Produce written reports For those involved, critical appraisal. For enforcement For wider publication

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Outbreak Preplanning External; Multidisciplinary. Internal; Robust protocols PHL, HSE,SWA. Annual

11 major enteric outbreaks 58 minor incidents

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Role of Outbreak Control Team (OCT).

Prelim. Assessment. Case ascertainment Hypothesis

Descriptive studies Analytical studies Special studies

Control measures

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Emergency Plan for Outbreaks OCT; roles, responsibilities and

legislation. Multidisciplinary Strategy to investigate and manage,

SOP. Risk assessment, Interventions, Monitor

effectiveness. Adequate surge resources. Communication: internal, external,

media.

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OCT Meetings minuted. Multidisciplinary updates. Continuous reassessment of public

health risk. Rationale for interventions, agreed,

designated and time frame. Conclusion, Debriefing, lessons learnt. Recommendations to prevent

recurrence. Outbreak report.

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Initial OCT Meeting Confirm:

PHL sample receipt requirements Pathogen analysis. Health and safety issues PHL result communication, format,

status, to whom. Clinical advice and interpretation Pathogen/sample storage PHL liason person attending OCT.

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OCT Meetings (Lab.) Provide update on lab.results. Provide specialist result

interpretation. Advise on pathogen related risk

assessment. Advise on infection control. Advise on interventions.

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PHL Outbreak Plan Notification, Outbreak code. Specimen receipt

Urgency, quantity, type. Time and mode of delivery Pathogen screen Request details, O/B code, GP,

contact Nos. Documented chain of custody Rejection criteria

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Health and Safety Advice For patient sample procurement For sample collector Sample packaging and transport At lab. reception During analysis Sample disposal

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Internal Laboratory Briefing

Clarify nature of outbreak. Outbreak code Designate Senior Technologist as

Outbreak Co-ordinator. Confirm agreed communication

route with OCT. Methodology, IQC and safety.

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Briefing cont. Establish potential sample numbers Devise outbreak staff rota and duties. Consider deferring routine work. Do stock audit. Review lab. space. Documentation; Receipt,Tech. work. Document daily dispatch of cumulative

validated results to agreed personnel.

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Reference Laboratory Establish early communication. Source of advice. Clarify:

Typing methods Turnaround time Urgency PHL contact person

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Outbreak conclusion Attend debriefing. Assess lab. response. Review lessons learnt. Modify lab. plan if necessary.

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Investigation of a Outbreak.

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Index Case

19 Y/O Admitted SHB Bloody Diarrhoea

23/6/04 Fri. 25/6/04 PHD notified ?E.coli

0157. What next?

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Day 1

Confirm VTEC Farm-Fork investigation, sporadic

case. Exposure Hx.

Dietary Water Recreational Occupational

Initiate investigation.

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Day 1 cont.

P H Dept, SHB link to NEHB EHO’s SHB, MWHB, NEHB

MWHB- Restaurant NEHB- Sports ground

PHL,SWAHB notified of case and samples

Interventions?

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Interventions Day 1.

MWHB, Restaurant inspection and sampled

NEHB, Sports ground. 2 pitches Intercounty Summer festival

tournament. Private well Water sampled Drinking water ceased imediately.

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•26/6 Sat, No. of foods and waters received PHL

•28/6 Day 4,

• Isolate index case received from SHB.

• Index case + Bar water confirmed as E. coli O157 VT1 + VT2 positive. PCR.

•What next?

Outbreak Day 4

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• Outbreak Situation Develops• OCT Co-ordinates• Public Health Laboratory Investigation• Public Health Interventions

Public Health Response Dynamic

OCT: PH Doc, EHO, Med Micro PHL, NDSC

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Outbreak Strands

Epidemiology, PHDept.

Case ascertainment

Epi curve Epi. Studies

Case Control Cohort

Interventions

Environmental, EHO,s

Premises inspection.

Operational review.

Sampling Interventions Closure?

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Premises

•Sports grounds

•Recent Tournaments

•Playing/training pitches

•Club house

•Investigations?

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Case Date(recvdPHL)

Potential source

Lab findings

Index 28/6, Water E. Coli O157, VT1+2 positive

Case 2 5/7, Water E. Coli O157, VT1+2 positive

Case 3 7/7 Water E. Coli O157, VT1+2 positive

Case 4 9/7 Water E. Coli O157, VT1+2 positive

Date exposed

19/6

25/6

25/6

25/6

All cases exposed at sports grounds

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Linked Cases

Public Health

•Sports festival 100+ kids 21/6-26/6

•Case assertainment

•Symptomatic Tested

•Asyptomatic not tested, advice given to them and GPs

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Water source

Date General water Microbiology findings (100mls)

IMS/PCR findings (1l)

Bar (potable)

26/6 E.coli=0

Col. Bact=0

E. Coli O157, VT1+ VT2

Bar (potable)

29/6 E.coli=0

Col. Bact=3

E. Coli O157, VT1+ VT2

Septic tank 6/7 E. Coli O157, VT1+ VT2

Surface water

15/7 E. Coli O157, VT1+ VT2

Interpret.ation?

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BAR(drinking water)

SEPTIC TANK

PRIVATE WELL

QUARRY

SURFACE WATER

ANNUAL RAINFALL

???

???

???

???

???

untreated

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Water Interventions

•Drinking alternative

•Treatment of private well: pre + post test samples

•Geographical Survey: dyeNo blackflow from septic tank

•Secure Private well.

•Other interventions?

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•Playing pitch fenced

•Training pitch not fenced

•Animals on training pitch

•No. of animal droppings sampled

•Clean grounds

•Washing hand notices

•Fence training pitch

Other Interventions.

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Sheep droppings

Received 14/7

• Non-O157,

•VT1 positive

•Interpret?

Other samples

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Other samples

14/7 clinical Sample

Contact of positive case

•Non-O157

•VT1 positive

•Interpret?

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 Lane 1: DNA ladderLane 2: Index case. Lane 3: Case 3. Lane 4: Case 2. Lane 5: case 4. Lane 6:Bar Water Lane 7: Septic tank Lane 8: Surface Water. Lane 9: DNA ladderLane 10: Sheep droppings. Lane 11: Sheep droppings. Lane 12: Sheep droppings. Lane 13: clinical non-O157 Lane 14: DNA ladder

PFGE

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Post intervention•Continue to screen water post treatment.

•Post treatment samples tested-Negative

•Enviromental water sampling?

Water source Date General water Microbiology findings (100mls)

Molecular biology findings (1l)

Surface water drain

20/7 Total coliform>24,192 cfu

E. Coli 7270 cfu

E. Coli O157 VT1+VT2 pos

Roadside Gully

14/9 E. Coli O157 VT2 pos

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Sample Serotype Genotype PT PFGE

Index O157 VT1+VT2 32 Pattern 1

Case 2 O157 VT1+VT2 32 Pattern 1

Case 3 O157 VT1+VT2 32 Pattern 1

Case 4 O157 VT1+VT2 32 Pattern 1

Bar O157 VT1+VT2 32 Pattern 1

Bar O157 VT1+VT2 32 Pattern 1

Septic tank O157 VT1+VT2 32 Pattern 1

Surface water O157 VT1+VT2 32 Pattern 1

Surface water drain O157 VT1+VT2 32 Pattern 1

Roadside gully O157 VT2

Clinical non-O157 O146 VT1 Pattern 3

Sheep droppings O75 VT1 Pattern 2

Sheep droppings O75 VT1 Pattern 2

Sheep droppings O75 VT1 Pattern 2

Sheep droppings O75 VT1 Pattern 2

Sheep droppings O75 VT1 Pattern 2

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Summary

•Water

•Indicator Micro. = Neg. VTEC POS

•Private Well vulnerability

•Environment- contamination of surface water

•Animal – recreational source

•Importance of Non-0157 diagnosis

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