Surveillance is the ongoing systematic collection, collation, analysis and interpretation of data and the dissemination of information to those who need to know in order that action may be taken.
Surveillance:
Collection
Analysis
Interpretation
Dissemination
Public Health Action:
Disease investigation, control and prevention
Planning and evaluation
Policy making
Surveillance can be active (special effort to collect data and confirm diagnoses) or passive (routine)
1. Detection of epidemics
2. Monitoring secular trends and identification of at-risk groups
3. Evaluation of an intervention
4. Monitoring control and prevention measures
5. Monitoring changes in infectious agents
6. Planning for the future and informing policy
7. Generating hypotheses and stimulation public health research
8. Archive of disease activity
1. Routine - e.g. notifications, COVER
2. Senitel - i.e. sample surveillance
3. Enhanced - TB, HIV/STIs, meningococcal disease
1. Establish Objectives
2. Develop case definitions
3. Determine data source or data collection mechanism
4. Develop data collection instruments
5. Field test methods
6. Data analysis and interpretation
7. Dissemination and feedback
8. Evaluation
Establish Objectives
Identifying high priority health events
Disease related:
Frequency (incidence, prevalence, mortality, morbidity)
Severity (case fatality, hospitalisation rate, QALYs)
Cost to society
Preventability
Communicability
Society related:
International obligations
Public & mass media interest
Political will to prevent
Availability of data
Establish case definitions
Criteria - i.e. person, place, time, clinical or laboratory diagnosis, epidemiological features
Sources of data
1. Lab reports
2. Statutory notifications
3. Hospital episode statistics
4. Clinical reporting - sentinel reporting system
5. COVER
6. Other clinical reports - e.g. BPSU, AIDS/HIV, KC60
7. Death certs
1. Describe the public health importance of the health event under surveillance consider:
Total numbers of cases, incidence and prevalence
Indices of severity (death rate, case fatality ratio)
Can it be prevented?
2. Describe the surveillance system to be evaluated
List its objectives (see purposes & uses of surveillance system)
Describe the health event under surveillance
Describe the components and operation of the system:
a. What information is collected?
b. Who collects the data?
c. Time to collect the data
d. Mode of data transfer and storage
e. Who analyses data?
f. How is it disseminated?
g. Who is it disseminated to?
3. Discuss validity and repeatability of case definitions in various types of surveillance data
4. Indicate the level of usefulness by describing the actions taken as a result of data collected by the surveillance system
5. Describe cost/resources needed to run surveillance
6. Evaluate the quality of the surveillance system by assessing its attributes
Flexibility
Representativeness
Acceptability
Timeliness
Sensitivity
Simplicity
7. List conclusions and recommendations
8. Ways to improve the system
Improve awareness of disease by increasing education
Simplify reporting
Frequent feedback
Use multiple sources and methods
Active surveillance
Sentinel surveillance
Computerisation
Feedback (distinguishes it from a database)
Rapidity
On-going
Standardised nature
Ease
Completeness
Accuracy
Relevance and/or representiveness
Timeliness
1. Statutory notifications
2. Lab reports
3. Death certs
4. Mycobnet
5. Enhanced tuberculosis surveillance
1. Hospital Episodes Statistics
2. Nursing, doctor notes
3, Lab reports and local lab based surveillance (MRSA, Clostridium difficile)
4. Surgical Site Infection Surveillance Service
1. Royal College of General Practitioners scheme
2. Mortality statistics
3. Lab reports
4, Hopsital Episodes Statistics
Incidence estimated from hospital admissions for unspecified community acquired pneumonia (CAP)
'Gold standard' surveillance
Monitoring trends - (1) annual data sets (UK/EWGLNET countries) (2) age groups (3) sex distribution (4) severity of illness and proportion of deaths (5) case type (6) method of diagnosis (urinary, serological, culture)
Local, regional, national and European surveillance [European Working group for Legionella Infections, Annual European report of all legionella cases (travel/nontravel) (EWGLI), International surveillance of travel associated legionnaires' diseases (EWGLINET)]
1. Systematic collection of data
2. Analyses of data to produce statistics (by time, person, place)
3. Interpretation to provide information (be aware of timeliness, completeness, representation)
4. Distribution of information to those who require action e.g. CDR weekly
5. Continuing surveillance to evaluate action