Passive surveillance includes data collection through various data notification systems
established by health departments as part of mandatory health law. Hospitals,
physicians, and laboratories report these data to local health departments. The CDC
issues yearly updates on notifiable diseases, with all resource agencies reporting on
either case diagnosis or suspicion.
Active surveillance includes actively searching for cases and inquiring directly with
individuals for signs and symptoms during epidemics or in a situation where an epidemic
is anticipated. Surveys are conducted to collect these types of data in the community.
The collected data are then analyzed and interpreted, with results disseminated
to professionals so that prompt action can be taken. Because infectious diseases do
not recognize any political border, an effective integrated and global public health
surveillance system is needed to counteract the potential evolution of an endemic to
an epidemic in this current world of globalization.