Epidemiological surveillance

Epidemiological surveillance is the discipline of continuously gathering, analysing, and interpreting data about diseases, and disseminating conclusions of the analyses to relevant organisations. As such, it is a key element in epidemiology.

Surveillance may be active or passive. In passive surveillance, no special effort is made to find unsuspected disease incidents. In contrast, screening programmes are a sort of active surveillance. Passive surveillance will usually only detect disease in those who get sick, meaning that healthy carriers and long incubation periods combined with passive surveillance can maintain a reservoir of undiscovered disease carrying agents.