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Distinct from screening.
Public health surveillance
Monitoring of levels of disease, (and sometimes, by extension, of activities to prevent or treat disease, such as vaccination) for the purposes of:
- Alert and Response - which requires rapid detection of threats to trigger rapid control measures. Clearly this requires systems which provide timely data; accuracy may be less important. For example, the WHO Alert and response system uses “rumours” from the media and informal sources to trigger further investigation and confirmation. See, for example HealthMap.
- Trend monitoring. Systems that focus on trend analysis, such as the uptake rates of vaccines or the number of cases of notifiable diseases, need accurate and complete data that need not be collected very frequently: frequency of collection will depend upon the system, but while data may be recorded as cases arise, for some systems data are collected every three months, or even less frequently.
Note that changes in disease incidence or prevalence can arise for all sorts of reasons; and often represent artefacts created by the information collection systems, rather than true changes in disease rates.
Surveillance of individual patients
Having identified, possibly through screening, a person who has a condition which may progress or become complicated, but at an unpredictable rate or time, surveillance may be indicated.