Principles of Surveillance

Lazareto de Mahón, Menorca, Spain

9th October 2006

EPIET 2004; Denise Werker

EPIET 2005; Suzanne Cotter

EPIET 2006; Susan Hahné

Content aim of lecture

context, definitions and history of surveillance

the process

aims of surveillance

criteria for undertaking surveillance

surveillance versus research

steps in setting up surveillance

challenges & opportunities

summary

After the lecture, you should be able to…Define: surveillance its three main components

Describe: the contexts / historical perspective of surveillance possible aims criteria for undertaking surveillance the difference between surveillance and research the different steps in setting up surveillance some challenges and opportunities

Aim

Context (1)

Presentations Principles of surveillance

Problem-based exercises Secular trends Surveillance

– set up surveillance – analytic tools for surveillance – evaluation of surveillance systems

Surveillance in EPIET Introductory Course

Intervention Epidemiology

Surveillance Outbreak investigation Applied epidemiological research

Context (2)

Control of Communicable Diseases: Tools isolation treatment disinfection & barriers quarantine & surveillance vaccination prophylaxis

Context (3)

Control of Communicable Diseases: Tools isolation treatment disinfection & barriers quarantine & surveillance vaccination prophylaxis

Context (3)

‘Close observation of individuals suspected of incubating serious infectious diseases in order to detect initial symptoms of disease in time to institute treatment and isolation’

Surveillancen. Close observation, especially of a suspected

spy or criminal

ORIGIN C19: from Fr., from sur- 'over' + veiller 'watch'

  Source: The Concise Oxford Dictionary. Ed. Pearsall J. Oxford University Press, 2001.

Definition - dictionary

Surveillance

“The continuing scrutiny of

all aspects of occurrence and spread of disease

that are pertinent to effective control”

Source: Last JM. A Dictionary of Epidemiology (Second Edition). Oxford University Press 1988, New York.

 

Definition – epidemiology (1)

Surveillance

“Continued watchfulness

over the distribution and trends of incidence,

through the systematic

collection, consolidation and evaluation of

morbidity and mortality reports and other relevant data

together with the timely and regular dissemination

to those who need to know”Source: Alexander Langmuir (1910 – 1993)

Definition – epidemiology (2)

William Farr (1807 – 1883) Superintendent, statistical department, General

Register Office, England and Wales Collected, analysed, interpreted vital statistics Plotted rise and fall of epidemics of infectious

diseases, identifying associations Disseminated information in weekly, quarterly,

and annual reports, medical journals, public press

First use for Public Health Action

Historical perspective (1)

21st World Health Assembly (1968) Systematic collection of pertinent data Orderly consolidation and evaluation of these

data Prompt dissemination of the results to those who

need to know

"Information for action"

Recognition by World Health Organization

Historical perspective (2)

Health Care System Public Health Authority

Event Data

InformationIntervention

Reporting

Capture

Analysis & Interpretation

Real world! … expected changes

Dissemination

Surveillance is a cyclical process

manage contacts of a case detect outbreaks early warning design/change vaccination policy design policy re antimicrobial resistance evaluate interventions to improve them certify elimination / eradication

Aims of Surveillance (1)

Actions: examples

Public Health aims Assess public health status (monitor trends,

detect outbreaks)

- prevent and control disease

Define public health priorities

- plan considering impact of hazard, exposure, disease

Evaluate public health programmes

- make decisions regarding interventions

Stimulate or inform research

- generate hypotheses, inform methodologie

Aims of Surveillance (2)

burden of disease (incidence / prevalence) severity, mortality epidemic potential, threat costs, socio-economic impact preventability / opportunities for control public concern and news-worthiness

Feasibility costs availability of data

Criteria for undertaking surveillance

Public Health importancePublic Health importance / rationale

Surveillance versus Research

Surveillance Applies existing knowledge to guide health

authorities in the use of known control measures Directly relevant to monitoring and control needs

Research Pursues new knowledge from which better

control measures will result Systematic investigation, testing and evaluation,

designed to develop or contribute to knowledge

1. Understand the problem

2. Identify opportunities for prevention & control

- interventions

- target audience

3. Set objectives

4. Specify requirements to meet objectives

5. Design- case definitions & indicators

- data needed

- data sources

- data transfer

Steps in setting up surveillance (1)

5. Translate information into action

- analyse

- interpret

- disseminate

6. Evaluate surveillance system

Steps in setting up surveillance (2)

Disease

DeathDisability

Recovery

Source of infection

Transmission

Reservoir

Vector

Environment

Direct

Exposure

Infection

1. Understand the problem

Infection

Disease

DeathDisability

Recovery

Source infection

Transmission

Reservoir

Vector

Environment

Direct

3. Treatment

4. Isolation/ treatment

2. Prophylaxis

6. Prevent transmission e.g. universal precautions

5. Ecological Management

Exposure

1. Vaccination

2. Identify opportunities for prevention & control

Public Health professionals Government / Politicians Clinicians / Microbiologists / Control of

Infection staff Environmental Health professionals Health service managers Health educators / teachers Public

2. Identify opportunities for prevention & control

Target audiences

Specific Measurable Acceptable and Action oriented Realistic Time related

3. Set objectives

SMART

3. Set objectives - examples

Vague... To estimate the prevalence of hepatitis C To detect outbreaks of measles

Specific, measurable, action-oriented & timed To assess the prevalence of hepatitis C in

France in order to allow planning of specific health care needs for the coming 20 years

To detect early time and place clustering of measles cases in order to ensure timely control of outbreaks

4. Requirements of the system

Keep it as simple as possible!! Timeliness Sensitivity Specificity Completeness of information Representativeness Acceptability

5. Design – case definitions

Exposed

Clinical specimen

Symptoms

Lab confirmed

Infected

Seek medical attention

Report

5. Design – examples of data needed

Numerators- number of cases- number of resistant strains

Denominators- population under surveillance- life births (CRS)- bacterial isolates (AMR)

5. Design – data sources (1)

Health service– notifications– laboratories– disease registries– community services– emergency services– screening programmes (antenatal, blood

donors)– pharmacy / over the counter drugs– vaccination programmes

5. Design – data sources (2)

Veterinary– animals (domestic, wild)– food

Environment– water– food– air

Population statistics– deaths– denominators

5. Design – data sources (3)

Issues cost

representativeness

comparability

confidentiality

acceptability

data quality

timeliness

commercial sensitivity

5. Design – data transfer

Existing infrastructure

Methods– web-based

– telephone

Frequency

Zero reporting

Sampling vs. comprehensive Aggregated vs. individual data Active vs. passive Statutory vs. voluntary Confidential vs. anonymous Security

5. Design – addition design issues

Analysis– descriptive (time, place, person)– time series– outbreak detection– molecular epidemiology – geographical information

systems (GIS)

Interpretation– system and data characteristics and changes– chance, bias, truth

6. Information into Action (1)

Dissemination of information– develop outputs in consultation with users– appropriate level of detail for action– regular review of usefulness– avoid information overload

6. Information into Action (2)

Did the system do what it set out to do?

7. Evaluation of surveillance system

Surveillance or research needed? Reliability

– crude and inaccurate

– incomplete

– accurate denominators

Sustainability– victim of success of control

New threats– emerging infections

– bioterrorism

Timeliness Human Rights

– data protection

Surveillance – the challenges

Near patient testing Less invasive diagnostics (oral fluid, urine) New molecular typing methods Electronic patient records ‘New’ data sources Behavioural surveillance Syndromic surveillance On-line, web-based systems

– data entry– dissemination of information

New analysis methods– GIS– bio-informatics– modelling

Surveillance – the opportunities

Context– communicable disease control– epidemiology

Definition– ‘information for action’

General process– capture– analysis– dissemination

Aims Criteria to set up surveillance system

– public health importance– feasibility– difference between surveillance and research

Different steps Challenges and opportunities

Summary

Thank you!