Role of laboratory in surveillance
Role of the laboratory in
disease surveillance
May 2007
P I D E M I C A L E R T
Laboratory Training for FieldEEpidemiologists
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R E S P O N S E
Learning objectives
At the end of the presentation, participants should:
• Understand how the laboratory contributes to
epidemiological surveillance
• Understand the principles of laboratory-based surveillance
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Laboratory Training for FieldEEpidemiologists
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Laboratories and disease surveillance
Before 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
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Laboratory Training for FieldEEpidemiologists
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Early 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)
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Laboratory Training for FieldEEpidemiologists
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Outbreak detection
Outbreak detection by the laboratory
Outbreak detection with assistance from the laboratory
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Laboratory Training for FieldEEpidemiologists
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Outbreak 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 disseminated
over a large area
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Outbreak 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 surveillance
requires good communication between the
epidemiologists and the laboratories
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Laboratory Training for FieldEEpidemiologists
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Laboratory role during outbreaks
Laboratory 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
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Laboratory Training for FieldEEpidemiologists
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Laboratory role during outbreaks
For new and emerging pathogens:
•Identify
the pathogen
•Develop
•Patient
laboratory tests
treatment/management
SARS
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Laboratory Training for FieldEEpidemiologists
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Courtesy:
The University of Hong Kong
Monitoring endemic disease trends
Confirm diagnosis
• Case definitions that include laboratory criteria
Monitor resistance patterns
Monitor subtypes of a pathogen
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Laboratory Training for FieldEEpidemiologists
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Monitoring 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
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Invasive meningococcal infection
serogroups by year, France, 1985-2000
C
600
B
Number of cases
500
A
Unknown
400
300
200
100
0
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
2000
Year
Source : InVS and NRC for N. meningitis, Pasteur Institute, Paris
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Cases of malaria by species, Region A
1992-1996
600
500
Others
Faciparum
400
300
200
100
0
1992
1993
1994
1995
1996
The increased proportion of falciparum is an early warning
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Eradication/elimination monitoring
The elimination phase requires more specific tests as
positive predictive value decreases
Laboratory confirmed diagnosis
• Polio surveillance
• Measles
Typing helps identifying the origin
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Cases of polio where wild poliovirus
was isolated in children, District X
1980-1996
National
immunization day
250
Number of cases
200
National
immunization day
150
100
50
0
80
81
82
83
84
85
86
87
88
89
90
91
Years
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Laboratory Training for FieldEEpidemiologists
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92
93
94
95
96
Predicting future AIDS trends for
health service planning
Cases of AIDS in City X, 1990-2004
Number of cases
700
600
500
400
300
200
100
0
90
91
92
93
94
95
96
97
98
99
Years
P I D E M I C A L E R T
Laboratory Training for FieldEEpidemiologists
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R E S P O N S E
00
01
02
03
04
Monitoring TB control program to ensure
complete treatment and cure
Number of patients
Tuberculosis: new cases, treatment completion and cures,
District X, 1994-1997
2000
1500
Cases
Completion
Cure
1000
500
0
1994
1995
1996
1997
Years
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Laboratory Training for FieldEEpidemiologists
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Establishing laboratory support for
public 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
P I D E M I C A L E R T
Laboratory Training for FieldEEpidemiologists
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Establishing laboratory support for
public health surveillance
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
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Establishing laboratory support
for public health surveillance
Peripheral level objectives
• Diagnosis and early warning signals
Routine lab surveillance with intensification before
epidemic season
• Environmental monitoring
• Epidemic prone disease monitoring
• Proper collection, transport and storage of samples
• Reporting of results
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Laboratory Training for FieldEEpidemiologists
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Establishing laboratory support
for public health surveillance
Intermediate level objectives
• Diagnosis and early warning signal
• Epidemic preparedness, response and capacity building
In addition to activities at peripheral level, strengthen
surveillance through:
• Supplies and logistics support
• Networking of laboratories, feedback and feed forward
• Monitoring, supervision
• Outbreak investigation, epi-lab coordination
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Laboratory Training for FieldEEpidemiologists
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Establishing laboratory support
for public health surveillance
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
P I D E M I C A L E R T
Laboratory Training for FieldEEpidemiologists
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Surveillance: 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
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Laboratory Training for FieldEEpidemiologists
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Surveillance: Lab functions
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
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Laboratory Training for FieldEEpidemiologists
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Surveillance: Lab & epi functions
Outbreak 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
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Laboratory Training for FieldEEpidemiologists
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Public health and clinical labs
Public 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)
P I D E M I C A L E R T
Laboratory Training for FieldEEpidemiologists
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Role of laboratory in surveillance
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
P I D E M I C A L E R T
Laboratory Training for FieldEEpidemiologists
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