When to Initiate Case Investigation and Contact Tracing Activities

Case investigation and contact tracing activities should be implemented at two distinct points in an epidemic:

•  First, early on in an epidemic, during the containment phase, case investigation and contact tracing are needed to stop transmission and prevent a large outbreak from occurring. If efforts to contain the epidemic are unsuccessful and widespread transmission occurs in the community, then stricter community mitigation measures (such as stay-at-home orders, business closures, etc.) must be implemented. If the strict mitigation measures are effective, transmission will begin to decline, and the community will enter a suppression phase.
• Second, once the community enters the suppression phase of the epidemic, the jurisdiction should begin to implement or scale up case investigation and contact tracing activities before the mitigation measures are fully lifted, in order to continue to reduce community transmission.

The decision to initiate or scale up COVID-19 case investigation and contact tracing activities will be unique to each area and will depend on the level of community transmission, characteristics of the community and their populations, and the local capacity to implement case investigation and contact tracing. It is critical that case investigation and contact tracing activities be adequately resourced and widely accepted in any community where they are implemented.

When a jurisdiction does not have the capacity to investigate a majority of its new COVID-19 cases, case investigation and contact tracing may not be the most effective approach. At that point, jurisdictions should consider suspending or scaling down contact tracing activities and reimplementing strict mitigation measures (such as stay-at-home orders, business closures, and school closures) until transmission begins to decline.