Principles of Surveillance

Lazareto de Mahón, Menorca, Spain

11 October 2011

Katharina Alpers (2009), Martin Donaghy (2008), Susan Hahné (2007, 2006),

Suzanne Cotter (2005), Denise Werker (2004)

Content

aim of lecture

surveillance: context, definitions and history

aims of surveillance

the process

surveillance versus research

steps in setting up surveillance

criteria for undertaking surveillance

challenges & opportunities

summary

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

Intervention Epidemiology

Surveillance Outbreak investigation Applied epidemiological research

Surveillance in EPIET Introductory Course

Lectures Principles of surveillance Event-based surveillance Analytical tools in surveillance Evaluation of a surveillance system H1N1 surveillance in Europe

Case studies Implementation of H1N1 surveillance Surveillance data analysis Evaluation of surveillance systems

The Concise Oxford Dictionary

n. Close observation, especially of a suspected spy or criminal

ORIGIN French, from sur- 'over' + veiller 'watch'

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

s 've l( )ns

Tools for Control of Communicable Diseases isolation treatment vaccination prophylaxis disinfection quarantine surveillance

‘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’

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

General Register Office, England and Wales Collected, analysed, interpreted vital statistics Described epidemics of infectious diseases Drew conclusions, made recommendations Disseminated information

First use of data for Public Health Action

“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”

Definition by Alexander Langmuir (1910 – 1993)

Systematic collection of pertinent data Orderly consolidation and evaluation of these

data Prompt dissemination of the results to those who

need to know

21st World Health Assembly (1968)

"Information for action"

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

- take decisions regarding interventions

Stimulate or inform research

- generate hypotheses, inform methodologie

Aims of Surveillance

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

Examples for Interventions

Health Care System Public Health Authority

Event Data

InformationIntervention

Reporting

Capture

Analysis & Interpretation

Real world! … expected changes

Dissemination

Surveillance is a cyclical process

Surveillance versus ResearchSurveillance 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

What we have seen so far

Contexts of surveillance Historical perspective Definitions Aims Three main components Surveillance versus research

1. Understand the problem

2. Identify opportunities for prevention & control

- interventions

- target audience

3. Set objectives

4. Specify attributes to meet objectives

5. Design- case definitions & indicators

- data needed

- data sources

- data transfer

Steps in setting up surveillance (1)

6. Translate information into action

- analyse

- interpret

- disseminate

7. Evaluate surveillance system

Steps in setting up surveillance (2)

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

Feasibility costs availability of data

1. Understand the problem- Criteria for priority setting

Public Health importance

Infection

Disease

DeathDisability

Recovery

Source infection

Transmission

Reservoir

3. Treatment

2. Prophylaxis

6. eg. hygiene precautions, vector control

5. Ecological Management

Exposure

1. Vaccination

2. Opportunities for intervention

4. Isolation/ treatment

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

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

3. 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. Attributes of the system

Timeliness Sensitivity Specificity Completeness of information Representativeness Acceptability

Keep it as simple as possible!!

Sentinel vs. comprehensive Aggregated vs. individual data Active vs. passive Statutory vs. voluntary Confidential vs. anonymous Basic vs enhanced Indicator based versus event based Security

5. Design – options

5. Design – examples of data needed

Numerators

- number of cases

- number of resistant strains

Denominators

- population under surveillance

- live births (CRS)

- bacterial isolates (AMR)

5. Design – case definitions

Exposed

Clinical specimen

Symptoms

Lab confirmed

Infected

Seek medical attention

Report

Case Definition

-Confirmed – Positive laboratory result

-Probable – Clinical + epidemiological link to confirmed case

-Possible - Clinical symptoms and signs

Demographics

-Person, place and time

Risk Factors

-Exposures

-Behaviours

Administrative

-Time reported

-Source

5. Design – data set

5. Design – issues

cost

representativeness

comparability

confidentiality

acceptability

data quality

timeliness

commercial sensitivity

5. Design – data sources: health services

– Laboratories: frontline diagnostic, reference– Clinical services: physicians,

hospital discharge data, disease registries– Screening programmes

(antenatal, blood donors)– vaccination programmes– pharmacy / over the counter drugs

5. Design – other data sources

Veterinary– animals (domestic, wild)– food

Environment– water– food– air

Population statistics– deaths– denominators

5. Design – data transfer

Existing infrastructure

Methods

– Paper

– Telephone

– Electronic

– Web-based

Frequency

Zero reporting

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

systems (GIS) Interpretation

– system and data characteristics and changes– chance, bias, truth– Public health significance

6. Information for Action (1)

Dissemination of information– develop outputs in consultation with users– Who needs to know what?– timing– appropriate level of detail– regular review of usefulness– avoid information overload

6. Information for Action (2)

6. Dissemination of information

Alerts-National and local -Europe: EWRS -International: IHR

Reports -Bulletins -Annual statements-Scientific journals

Internet Public

-media

Does the system do what it set out to do?

i.e. meet specified objectives:

Contribute to achieving public health goals?

Meet the needs of stakeholders to improve policy, services, public understanding?

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

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

Opportunities

Context– communicable disease control– epidemiology

Definition– systematic collection of data– information for action

Aims Process with 3 components

– capture– analysis– dissemination

Difference between surveillance and research Criteria and steps to set up surveillance system

– public health importance– feasibility– information for action

Challenges and opportunities

Summary