Laboratory Training for Field Epidemiologists Role of the laboratory in disease surveillance Role of...

E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists

Role of the laboratory in disease surveillance

Role of laboratory in surveillance

May 2007


Learning objectivesLearning objectives

At the end of the presentation, participants should:

• Understand how the laboratory contributes to epidemiological surveillance

• Understand the principles of laboratory-based surveillance


Laboratories and disease surveillanceLaboratories and disease surveillanceBefore the outbreak

• Early warning signals

• Outbreak detection

During the outbreak

• Outbreak response and management

In between outbreaks

• Trend monitoring

• Intervention evaluation

• Monitoring progress towards a control objective


Early warning signalsEarly warning signals

Detection of pathogens that have potential to spread

Sentinel events requiring early control measures

• Isolation of a single epidemic prone isolate (e.g. non-typhoidal salmonella isolated from a neonate in a hospital neonatal intensive care unit)

• Emergence of resistant strains in the hospital or the community (e.g. multi-drug resistant tuberculosis)


Outbreak detection Outbreak detection

Outbreak detection by the laboratory

Outbreak detection with assistance from the laboratory


Outbreak detection by the labOutbreak detection by the lab

Identification of a cluster of:

• Infections with an unusual pathogen

• Specific subtype of a pathogen

– Outbreak of antibiotic-resistant strains

– Subtypes of a pathogen (e.g. Shigella dysenteriae type I)

Reference centres may capture outbreaks disseminatedover a large area


Outbreak detection with lab helpOutbreak detection with lab help

Epidemiologist captures an increased incidence

Laboratory:

• Confirms the diagnosis

• Allows for a more specific case definition

• Detects a new pathogen

• Provides additional details on the pathogen (e.g., phage type)

Effective participation of the laboratory in surveillancerequires good communication between theepidemiologists and the laboratories


Laboratory role during outbreaksLaboratory role during outbreaksLaboratory confirmation of early cases

• On a subset of cases

Identification of new pathogens

Typing of the pathogen

• Link clusters when the epidemiological data is not sufficient

Antimicrobial susceptibility testing to guide treatment

Post-outbreak surveillance

Environmental investigations

Detection of carriers


Laboratory role during outbreaksLaboratory role during outbreaks

For new and emerging pathogens:

•Identify the pathogen

•Develop laboratory tests

•Patient treatment/managementSARS

Courtesy:The University of Hong Kong


Monitoring endemic disease trendsMonitoring endemic disease trends

Confirm diagnosis

• Case definitions that include laboratory criteria

Monitor resistance patterns

Monitor subtypes of a pathogen


Monitoring endemic disease trendsMonitoring endemic disease trends

Examples:

Circulating strains of bacterial meningitis

• Impact on treatment protocols

• Impact on immunization policies

Antibiotic resistance

• Methicilin resistant staphylococcus aureus

• Vancomycin resistant enterococcus

• Tuberculosis


0

100

200

300

400

500

600

85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 2000

Year

Num

ber o

f cas

es

C

B

A

Unknown

Source : InVS and NRC for N. meningitis, Pasteur Institute, Paris

Invasive meningococcal infection Invasive meningococcal infection serogroups by year, France, 1985-2000serogroups by year, France, 1985-2000


0

100

200

300

400

500

600

1992 1993 1994 1995 1996

Others

Faciparum

Cases of malaria by species, Region A Cases of malaria by species, Region A 1992-19961992-1996

The increased proportion of falciparum is an early warning


Eradication/elimination monitoring Eradication/elimination monitoring

The elimination phase requires more specific tests aspositive predictive value decreases

Laboratory confirmed diagnosis

• Polio surveillance

• Measles

Typing helps identifying the origin


0

50

100

150

200

250

80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96

Years

Nu

mb

er

of c

ase

s

National immunization day

National immunization day

Cases of polio where wild poliovirus was Cases of polio where wild poliovirus was isolated in children, District X 1980-1996isolated in children, District X 1980-1996


Predicting future AIDS trends for Predicting future AIDS trends for health service planninghealth service planning

Cases of AIDS in City X, 1990-2004

0

100

200

300

400

500

600

700

90 91 92 93 94 95 96 97 98 99 00 01 02 03 04

Years

Num

ber o

f cas

es


Tuberculosis: new cases, treatment completion and cures, District X, 1994-1997

0

500

1000

1500

2000

1994 1995 1996 1997

Years

Num

ber o

f pat

ient

s

Cases

Completion

Cure

Monitoring TB control program to ensure Monitoring TB control program to ensure complete treatment and curecomplete treatment and cure


Establishing laboratory support for Establishing laboratory support for public health surveillancepublic health surveillance

Identify diseases of public health importance

List diseases that require laboratory confirmation

Determine tests to be performed

Map laboratory facilities and human resources,including reference laboratories

Establish laboratory networking

Identify a focal person to coordinate laboratory activities

Determine information flow


Define roles and responsibilities, identify referral system

Ensure supplies, logistics, guidelines and forms

Organize communication between lab and epi

• Prompt, regular reporting of results and feedback

Plan quality assurance, biosafety and waste management

Supervise and monitor

Develop epidemic preparedness and response plans



Peripheral level objectives

• Diagnosis and early warning signals

Routine lab surveillance with intensification beforeepidemic season

• Environmental monitoring

• Epidemic prone disease monitoring

• Proper collection, transport and storage of samples

• Reporting of results



Intermediate level objectives

• Diagnosis and early warning signal

• Epidemic preparedness, response and capacity building

In addition to activities at peripheral level, strengthensurveillance through:

• Supplies and logistics support

• Networking of laboratories, feedback and feed forward

• Monitoring, supervision

• Outbreak investigation, epi-lab coordination



Referral level objectives

• Confirmation and capacity building

Key activities

• Referral investigations

• Outbreak investigation

• Development of guidelines

• Quality assurance program, bio-safety and waste management

• Training, monitoring, supervision and feedback



Surveillance: Lab functionsSurveillance: Lab functions

Confirmation of etiology to resolve syndromic presentation

Data intelligence for:

• Antimicrobial resistance monitoring

• Emergence of unusual isolates

• Detection of new pathogens

• Sero-surveillance


Outbreak detection within the laboratory

Tracing spread through typing and characterization

Detection of carriers and natural foci of infection

Determine the end of an outbreak

Determine elimination or eradication of disease

Surveillance: Lab functionsSurveillance: Lab functions


Surveillance: Lab & epi functionsSurveillance: Lab & epi functionsOutbreak detection and investigation

Develop case definition; determine case management

Environmental monitoring

Understand the natural history of disease

Evaluate interventions

Monitor progress towards control

Develop immunization strategies

Prevalence studies


Public health and clinical labsPublic health and clinical labsPublic health laboratories

• Belong to the public sector

• Are involved in public health

• Participate in surveillance

Clinical laboratories

• May be public or private

• Involved in management of patients

• May participate in public health surveillance (e.g. laboratory reporting)


Developed by the Department of Epidemic and Pandemic Alert and Response of the World Health Organization with assistance from:

European Program for Intervention Epidemiology Training

Canadian Field Epidemiology Program

Thailand Ministry of Health

Institut Pasteur

Role of laboratory in surveillance

Laboratory Training for Field Epidemiologists Role of the laboratory in disease surveillance Role of...

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