The World Health Organization (WHO) defines public health surveillance as the “continuous, systematic collection, analysis and interpretation of health-related data needed for the planning, implementation, and evaluation of public health practice.

A health problem must be well defined before it can be solved. Surveillance systems generate data that help public health officials understand existing and emerging infectious and non-infectious diseases. Without a proper understanding of the health problem, it will be difficult to ameliorate the health issue.

The main types of information collected by surveillance systems to measure the relative importance of a disease are:

Incidence/prevalence

Severity (case fatality rate)

Mortality rate

Productivity loss

Premature mortality (YPLL)

Costs in medical care

Preventability of disease