Passive surveillance is characterized by:

• A. Relies on routine reporting by professionals; inexpensive but prone to error
• B. Active solicitation of case reports; expensive
• C. Uses sentinel sites; warning system; no precision
• D. Migrant tracking programs

Answer: (A)

Passive surveillance relies on routine reporting by clinicians and laboratories. Because it uses existing health-care interactions and standard reporting channels, it is inexpensive to operate. But it often misses cases that aren’t diagnosed or reported, and reports can be delayed, incomplete, or inconsistent, which makes the data prone to underreporting and error. This approach helps monitor trends over time and across large populations at low cost, but it isn’t ideal for precise incidence estimates or rapid outbreak detection.

Active surveillance would involve proactively seeking out cases and collecting data, which explains its higher costs. Sentinel surveillance uses selected sites to monitor disease signals rather than the whole population, offering early warning but not full coverage. Migrant tracking programs focus on movement patterns rather than comprehensive disease reporting.