Surveillance Flashcards
What is surveillance?
Systematic ongoing data collection
Give 5 reasons why surveillance may be carried out
Determine the impact of disease
Detect changes in disease patterns and gather timely feedback
Monitor effectiveness of preventative/control measures
Identify outbreaks
Detect new disease
Monitoring and evaluation
Gives aetiological clues
Give 4 examples where surveillance would be essential
Identifying the effects of a mass vaccination programmes
Effect of introducing sanitation/clean water supplies on diarrhoea
Controlling an epidemic by withdrawing contaminated food
Monitoring Legionnaries after a law on maintenance of cooling towers
Why can surveillance not be solely relied on?
It only gives a proxy measure of disease
If it covers a large area/population it is likely to miss small changes
Rarely able to measure disease incidence
What is passive surveillance and when is it used?
Routine data collection from lab tests
Most commonly used -for diseases with background rates
What is sentinel surveillance and when is it used?
Use of reporting sources at different sites across an area
Works best for common diseases
What is enhanced surveillance and when is it used?
Certain regions are selected to report on a certain disease within a certain time period - quite specific and suitable for common infections (TB, meningitis, influenza etc.)
What is active surveillance and when is it used?
When active completeness of reporting is required - involved reporting known cases and also reported number of no cases
What are the main stages of a surveillance programme?
- Data collection - needs a case definition and known sources of data and method of collection
- Data analysis-use epidemiologist to show stats
- Interpretation - look for true trends, risk factors and decide on if something is an outbreak
- Response - preventative and control measures to limit spread of disease
What could be the reason for changes in surveillance data?
A true change in incidence of a disease (due to an outbreak or seasonal variation)
Artefactual - incorrect recording of data
Change in diagnostic metod
Change in observer/data collecter
Random variation
Name 5 diseases that may require international surveillance
Legionnaires E.coli Salmonella Cholera SARS hep A Meningococcal infection AIDS/HIV
What about a disease may surveillance be reporting?
Morbidity
Mortality
Lab results - incidence
Outbreak
What are a vaccine may surveillance be reporting?
Utilisation
Efficacy
Side-effects
What factors of a disease must be considered in surveillance implementation?
Biological functions of the disease
Biological changes in an agent of disease
Reservoirs of the infection
Vectors of the infection
Environmental/occupational factors affecting the disease
Social disease determinants/lifestyle
What are the advantages and disadvantages of passive surveillance?
Advantages - relatively cheap, enables constant monitoring and data collection
Disadvantages - incompleteness, inaccuracy and timeliness (units not reporting on time)
If reporting behaviour changes this can change incidence rates which don’t reflect a true change in incidence
What are the advantages and disadvantages of sentinel surveillance?
Usually sentinel general practices have an incentive so may be more reliable in reporting
Works well for viral GE, chickenpox, influenza (common)
Works less well for rare diseases
Give 5 situations where active surveillance is likely to be useful
Rare conditions
Serious/highly contagious disease - SARS, Ebola
Monitoring vaccine failure eg: Hib
If the goal is disease eradication eg: Polio in Nigeria
If public health interventions are required eg: meningococcal disease in the UK
Why is influenza not notifiable?
Difficult to clinically diagnose
Could overwhelm surveillance systems during epidemics/pandemics
No urgent action that can be taken
What type of surveillance is influenza likely to be under and why?
international - due to risk of pandemics
What type of surveillance is used for STIs?
Sentinel - use of GUM clinics
What type of surveillance is necessary for HCAIs?
Continuing passive - mandatory to report organisms causing HCAIs
