to detect changes in trends or
distribution of a disease or behaviours
leading to an increased risk of a disease
with the aim of facilitating disease control
In order to be effective, a
surveillance system must be:
practical, uniform, rapid
Common
approaches to
collect surveillance
data
Reporting of
notifiable diseases
Advantages:
comprehensive coverage,
cheap to run, enables action
to be taken quickly to
control outbreaks
Disadvantages: inaccuracy of
diagnosis because of a) lack of
standard clinical criteria for diagnosis
b) clinical diagnoses often used,
without laboratory confirmation,
incomplete (and possibly
unrepresentative), minimal data on
each case
Sentinel reporting schemes:
sample of primary care providers
asked to submit regular reports on
all cases of specified diseases
diagnosed within specified time
period
Advantages: more accurate; more
rapid; can get more data on each
case, which may include laboratory
data; can monitor trends
Disadvantages: less complete
coverage, and so will not identify
localised outbreaks or diseases
which only occur in a limited
geographical area; less useful for
rare diseases
Laboratory surveillance: Diagnostic
microbiology laboratories are asked
to report all identifications of
specified organisms to a central
agency.
Advantages: high diagnostic
accuracy; availability of
additional laboratory information
such as serotyping or patterns
of antibiotic resistance
Disadvantages: small sample of all cases,
which may be unrepresentative; strongly
influenced by pattern of laboratory use of
individual practitioners; limited clinical
information; only useful for diseases which
have a diagnostic test
Serological surveillance: examining
blood samples, usually provided for
another purpose, for antibodies to a
specific pathogen of interest
Periodic population-based
surveys: Population-based
surveys can provide
surveillance data if they are
repeated at regular
intervals.
important that such
surveys are conducted
using standardised
methods so that
comparisons over time are
valid
Syndromic surveillance to
detect unusual disease
clusters rapidly
Second generation
surveillance to improve the
use of surveillance in the
control of the HIV epidemic
Informal networks: WHO
manages the Global Alert and
Response Network (GAR) and
maintains a list of early reports of
potential outbreaks