Overview and Key Take Away

Case investigation and contact tracing are an essential part of the COVID-19 response pdf icon. Prompt isolation of people diagnosed with COVID-19, and identification and quarantine of close contacts, can effectively interrupt disease transmission and reduce spread of SARS CoV-2. When implemented quickly, contact tracing, along with other community mitigation efforts work together to reduce transmission. Where increases in COVID-19 cases strain resources, health departments may need to prioritize case investigation and contact tracing.

Health departments experiencing surge or crisis situations around COVID-19 should prioritize case investigation interviews of people who tested positive for or were diagnosed with COVID-19 in the past 6 days (based on specimen collection date or symptom onset, if known). They should also focus contact tracing efforts on:

  • household contacts exposed in the past 6 days, and
  • people living, working, or visiting congregate living facilities, high density workplaces or other settings (or events) with potential extensive transmission.

In some instances, further prioritization may be necessary.

People diagnosed with COVID-19 should be strongly encouraged to notify all their household contacts:

  • to immediately self-quarantine; and
  • to seek additional guidance from their health department or CDC’s COVID-19 website.

As resources allow, health departments should expand case investigation and contact tracing for people outside the household who:

As resources allow or COVID-19 case rates decline, health departments should:

  • expand case investigation interviews to people with positive COVID-19 test specimens collected in the past 14 days; and
  • expand contact tracing to all contacts exposed within the past 14 days.

If more than 14 days have elapsed since specimen collection, case investigation and contact tracing should not be pursued unless there are unique circumstances associated with the person tested (e.g., part of large outbreak associated with congregate living or high density workplace or work in a healthcare setting).

Audience

These prioritization recommendations are intended to assist state, tribal, local, and territorial health departments, particularly those with escalating COVID-19 case counts, delays in receipt of laboratory test results or healthcare provider reports, or with insufficient capacity to conduct case investigation and contact tracing for all newly reported COVID-19 cases in a timely manner.

Summary of Prioritization Recommendations

When health departments are facing a high burden of COVID-19 cases, they may not have the resources to complete timely case investigation and contact tracing activities for all reported cases of COVID-19. In these situations, prioritization of public health activities may become necessary. CDC’s Case Investigation & Contact Tracing Guidance suggests that when resources are limited, health departments should prioritize the most impactful public health activities. CDC’s COVID -19 Case Investigation and Contact Tracing Hierarchies outline priority populations for case investigation and contact tracing. These new recommendations are intended to provide additional information and an overview of prioritization strategies for consideration. Implementation of these recommendations should be guided by what is feasible, practical, and acceptable for each community.

As the burden of COVID-19 worsens in an area, and the capacity to investigate new cases in a timely manner becomes more difficult or is not feasible, health departments should prioritize which cases to investigate and which contacts to trace. In addition, health departments should emphasize broader community mitigation measures. Determining when burden is high will vary by area. Feasibility of case investigation and contact tracing is determined by the volume and trajectory of new cases, as well as staff resources and capacity.  Below are examples of how to assess an area’s capacity to conduct case investigation and contact tracing.

  • High burden could be defined as a backlog of cases for each interviewer that is at least twice the number (100% more) they are able to interview each day;
  • Medium burden could be defined as a backlog of cases for each interviewer that is 50% more than the number of cases they are able to interview each day;
  • Low burden could be defined as a reasonable number of cases for each interviewer to call each day.

When experiencing a high burden of cases, Figure 1 is a summary of recommendations that health departments could use to prioritize case investigation and contact tracing activities.

Figure 1

Highest Priority  Activities

For cases, prioritize case investigations for people  diagnosed with COVID-19 in the past 6 days

(based on specimen collection date or symptoms onset, if known)

For contacts, prioritize:

  • Household contacts exposed in the past 6 days
  • People living, working, or visiting congregate living facilities, high density workplaces or other settings (or events) with potential extensive transmission

Next Level Priority Activities

As resources allow, expand case investigations and contact tracing to people outside the household who are:

  • At increased risk for severe illness
  • Part of a cluster
  • Exposed within the past 6 days

Low Priority Activities

  • As resources allow or COVID-19 case rates decline, expand case investigation interviews to people with positive COVID-19 test specimens collected in the past 14 days, and expand contact tracing to all contacts exposed within the past 14 days
  • If more than 14 days have elapsed since specimen collection, case investigation and contact tracing should generally not be pursued



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