What’s the difference between “diagnostic” and “surveillance” Covid-19 testing?

The Centers for Disease Control and Prevention defines these kinds of tests this way:

  • Diagnostic testing for SARS-CoV-2 is intended to identify occurrence at the individual level and is performed when there is a reason to suspect that an individual may be infected, such as having symptoms or suspected recent exposure, or to determine resolution of infection.
  • Surveillance testing is generally used to monitor for a community- or population-level occurrence, such as an infectious disease outbreak, or to characterize the occurrence once detected, such as looking at the incidence and prevalence of the occurrence. Surveillance testing is used to gain information at a population level, rather than an individual level.