Field Epidemiology in Field Epidemiology in Practice: A Hospital Practice: A Hospital Outbreak of Outbreak of Acinetobacter Acinetobacter Suzanne Beavers, M.D Suzanne Beavers, M.D EIS Officer EIS Officer Kentucky Department for Kentucky Department for Public Health Public Health
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Field Epidemiology in Practice: A Hospital Outbreak of Acinetobacter Suzanne Beavers, M.D EIS Officer Kentucky Department for Public Health.
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Field Epidemiology in Field Epidemiology in Practice: A Hospital Practice: A Hospital Outbreak of Outbreak of AcinetobacterAcinetobacter
Suzanne Beavers, M.DSuzanne Beavers, M.DEIS OfficerEIS OfficerKentucky Department for Kentucky Department for Public HealthPublic Health
EnvironmentDistribution and determinants of disease frequency . . .
. . . application to public health problems.
Why initiate an Why initiate an investigation?investigation? Characterize the problemCharacterize the problem Control and preventionControl and prevention Research-answer scientific Research-answer scientific
questionsquestions Training of epidemiologistsTraining of epidemiologists Political/legal requirementPolitical/legal requirement
10 Steps of a Field 10 Steps of a Field InvestigationInvestigation
1.1. Prepare for field workPrepare for field work
2.2. Establish existence of outbreakEstablish existence of outbreak
3.3. Verify diagnosisVerify diagnosis
4.4. Define and identify casesDefine and identify cases
5.5. Orient data in terms of time, place, personOrient data in terms of time, place, person
6.6. Develop hypothesesDevelop hypotheses
7.7. Evaluate hypothesesEvaluate hypotheses
8.8. Plan additional studiesPlan additional studies
9.9. Implement control and prevention Implement control and prevention measuresmeasures
10.10. Communicate findingsCommunicate findingsAdapted from Field Epidemiology ed. Gregg MB
Field Investigations in Field Investigations in Healthcare FacilitiesHealthcare Facilities Infections common, epidemics Infections common, epidemics
uncommonuncommon Patients highly susceptible to Patients highly susceptible to
Traditionally Traditionally associated with associated with ICUsICUs
Increasing cause Increasing cause of serious illnessof serious illness
Image courtesy of Acinetobacter.com
MicrobiologyMicrobiology
Ubiquitous:Ubiquitous:– Widely distributed in nature (soil, water, Widely distributed in nature (soil, water,
food, sewage) & the hospital environmentfood, sewage) & the hospital environment Survive on moist & dry surfacesSurvive on moist & dry surfaces 32 species32 species
– >2/3 of >2/3 of AcinetobacterAcinetobacter infections are due infections are due to to A. baumanniiA. baumannii
Major infections due to Major infections due to AcinetobacterAcinetobacter Ventilator-associated pneumonia Ventilator-associated pneumonia Urinary tractUrinary tract Bloodstream infectionBloodstream infection Skin/wound infectionsSkin/wound infections EndocarditisEndocarditis PeritonitisPeritonitis
related to ventilatorsrelated to ventilators– Variety of other sources Variety of other sources
recognized, including cell phones, recognized, including cell phones, mattresses, Bear huggers, mattresses, Bear huggers, common source medicationscommon source medications
*Ryan MP, et al, 2006 **Coenye T, et al, 2002 and Vaneechoutte M, et al, 2001
Acinetobacter Acinetobacter Outbreak InvestigationOutbreak InvestigationVerify existence of Verify existence of outbreakoutbreak DPH notified in October, 2006DPH notified in October, 2006 Hospital A in KY has increased Hospital A in KY has increased
number of casesnumber of cases 75 patients with culture-positive 75 patients with culture-positive
Acinetobacter since January, Acinetobacter since January, 20062006
Verify DiagnosisVerify Diagnosis
Goal is to rule out:Goal is to rule out:
misdiagnosismisdiagnosis
laboratory errorlaboratory error Examine case-patientsExamine case-patients Review medical recordsReview medical records Confirm laboratory testingConfirm laboratory testing
Identify and Count Identify and Count CasesCases Goals:Goals:
– Identify maximum number of casesIdentify maximum number of cases– Exclude noncasesExclude noncases
Consider spectrum of manifestation Consider spectrum of manifestation (colonized vs infected)(colonized vs infected)
Develop Case DefinitionDevelop Case Definition– Set of conditionsSet of conditions– Specific time periodSpecific time period– Specific locationSpecific location
Identify and count Identify and count casescases Conduct Conduct
systematic systematic searchsearch
Use multiple Use multiple sourcessources
Construct a line Construct a line listlist
Orient DataOrient Data
PersonPerson
PlacePlace
TimeTime
Time-Ordering Key Time-Ordering Key EventsEvents Onset of illness in cases and Onset of illness in cases and
contactscontacts Period of exposure to causal Period of exposure to causal
agents or risk factorsagents or risk factors When treatments beganWhen treatments began When control measures When control measures
implementedimplemented Potentially related events or Potentially related events or
unusual circumstancesunusual circumstances
TimeTime
Epidemic curve: # of cases by time Epidemic curve: # of cases by time of onsetof onset
Configuration permits inferencesConfiguration permits inferences– Agent known: use incubation period to Agent known: use incubation period to
look back at exposurelook back at exposure– Agent unknown, but common event Agent unknown, but common event
likely: postulate agent by determining likely: postulate agent by determining the incubation periodthe incubation period
• Construct relative to specific sites or Construct relative to specific sites or groupsgroups
Acinetobacter Acinetobacter outbreakoutbreak
Figure 1. Frequency of Acinetobacter cases at Hospital B by half month from April -
October 2006
0
1
2
3
45
6
7
8
9
Culture Date
Co
un
t
PlacePlace
In a general outbreak:In a general outbreak:– Place of residencePlace of residence– Place of occupationPlace of occupation
In a healthcare setting:In a healthcare setting:– Floor or unitFloor or unit– Operating roomOperating room
PersonPerson
Thoroughly describe the case Thoroughly describe the case groupgroup
Identify factors shared in Identify factors shared in common by casescommon by cases
Obtain denominators to Obtain denominators to derive ratesderive rates
Compare groupsCompare groups
Formulate and test Formulate and test hypothesishypothesis Goal: explain the problemGoal: explain the problem
Use comparison group(s)Use comparison group(s)– Case-control studyCase-control study– Cohort studyCohort study
• Consider causationConsider causation
Compare Hypothesis Compare Hypothesis with established factswith established facts Environmental/staff cultures Environmental/staff cultures
may be neededmay be needed– Performed to aid in the Performed to aid in the
investigation once theories are investigation once theories are generatedgenerated
– Less valuable in generating Less valuable in generating hypotheseshypotheses
Plan More Systematic Plan More Systematic StudyStudy Control Control
measuresmeasures Continued Continued
data analysisdata analysis
Implement Control Implement Control MeasuresMeasures Eliminate/treat sourceEliminate/treat source Prevent further exposuresPrevent further exposures
– Active surveillanceActive surveillance Protect at-risk populationProtect at-risk population