Surveillance can be active or passive. In active surveillance, specific workers designated as surveillance workers are given target areas that they are supposed to visit once a fortnight. They enquire the following:
- Whether there is a case of fever in the house.
- Whether there was one between his previous visit and the present one.
The search for malaria cases by local health agencies such as primary health centers, sub–centers, hospitals, dispensaries and local medical practitioners is known as “Passive surveillance”. The passive agencies collect blood smears from all fever cases and also from those with a history of recent fever.