COVID-19 Case Investigation and Contact Tracing

Quick Takes

  • This study reviews contact tracing effort for COVID-19 by 13 health departments and one Indian Health Service unit.
  • Two of three individuals with COVID-19 were either not reached for interview or named no contacts when interviewed.
  • Contact tracing is resource-intensive and less effective in viral infections that are easily transmissible and have a significant proportion of pre- and asymptomatic spread such as COVID-19.

Study Questions:

What is the proportion of people with a positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) test and their contacts reached by public health authorities as part of contact tracing efforts?

Methods:

The authors examined data from 13 health departments and one Indian Health Service unit across 11 states and one tribal nation, selected to maximize variation in geography and population density. They used routinely collected COVID-19 case investigation and contact tracing data to quantify the number of people with a positive SARS-CoV-2 test reported for public health surveillance, how many were interviewed, and how many named contacts.

Results:

The total number of cases reported was 74,185. Of these, 43,931 (59%) were interviewed, and 24,705 (33%) named any contacts. Among the 74,839 named contacts, 53,314 (71%) were notified of their exposure (range across department 53-95%), and 34,345 (46%) agreed to monitoring. A mean of 0.7 contacts were reached by telephone by public health authorities, and only 0.5 contacts per case were monitored. The positive test prevalence among contacts varied and was higher in six locations compared to the general population, and lower in two locations. There were wide variations in key case investigations and contact tracings across departments. The median time from index case specimen collection to positive test report to the health department was 2 days (range, 1-5 days). The median time from index case specimen collection to contact notification was 6 days.

Conclusions:

In this cross-sectional study of US local COVID-19 surveillance data, the effectiveness of contract tracing varied significantly and is likely suboptimal given most cases were either not reached for interview or named no contacts when interviewed.

Perspective:

Contact tracing and quarantine of exposed contacts is essential in mitigating the spread of infectious pathogens. It is an inefficient and resource-intensive process, of which effectiveness invariably depends on the nature of the infection. Viral infections that are easily transmissible and have a significant proportion of pre- and asymptomatic spread such as COVID-19 pose a major challenge to contact tracing, as is evidenced in this study. These challenges, however, have prompted an increased reliance on digital health tools, and applications may help overcome barriers to contact tracing, which are likely to be more widely adopted in the next pandemic. Lastly, it is difficult to determine from this study whether the contact tracing efforts of the sample health departments have contributed positively to mitigation of disease spread. Nevertheless, contact tracing remains an important tool in the public health arsenal with very specific case uses.

Clinical Topics: Prevention

Keywords: Contact Tracing, Coronavirus, COVID-19, Diagnostic Tests, Routine, Monitoring, Physiologic, Pandemics, Population Density, Public Health, Public Health Surveillance, Primary Prevention, Quarantine, SARS-CoV-2, United States Indian Health Service, Virus Diseases


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