COVID-19 Contact Tracing in Two North Carolina Counties, June–July 2020

Summary

• Contact tracing works only if it is fast and communities take part.
• In summer 2020, as North Carolina's COVID-19 incidence rose 183% — from seven to 19 cases per 100,000 people a day during June 1–July 12 — CDC and the state examined contact tracing in Mecklenburg County (mostly Charlotte) and Randolph County.
• Many patients named no contacts, many contacts couldn't be reached, and contacts were notified a median 6 days after the patient's test. Faster tracing, community engagement and community-wide measures were needed.

How tracing worked

Health department staff interviewed people with confirmed COVID-19 to find close contacts, then called each contact to check for symptoms, told them to quarantine for 14 days after their last exposure, monitored them, and encouraged testing. People who didn't respond to three attempts on consecutive days, or had missing or wrong contact details, were counted as lost to follow-up.

What happened

• In Mecklenburg, results took a median 2 days, and 23% of patients were never reached. In Randolph, results took 3 days, and even sending law enforcement to the address didn't reach five patients.
• Some contacts who were reached declined monitoring: 255 (2%) in Mecklenburg and 50 (4%) in Randolph.
• In Randolph, 293 contacts in quarantine (53%) were tested, and 69 (24%) were positive; in Mecklenburg, 137 contacts were confirmed to have COVID-19 during follow-up.

Why so many gaps

• Telephone-only interviews may have made it hard to build rapport.
• Patients may have wanted to spare contacts quarantine and its costs, such as lost work.
• Contacts may not answer calls from unknown numbers.
• The sheer volume of cases strained staff.
• Mixed and sometimes conflicting public messages about COVID-19 precautions may have played a part.

The share naming no contacts was high compared with other infectious diseases before the pandemic, but similar to Maryland (50%) and New Jersey (52%), where about half of contacts were reached (50% and 54%). This points to weak community support for contact tracing, which, together with testing delays, fed ongoing spread.

North Carolina's response: the state health department hired more staff for local health departments, improved data systems, and adopted tools such as a single statewide caller ID number.

Limits: both counties were in a surge, which strains the system; data were self-reported, and people may have underreported contacts; and the reasons patients named no contacts, and contacts couldn't be reached, weren't recorded.

Sources

Based on R. Ryan Lash, Catherine V. Donovan, Aaron T. Fleischauer and others (CDC, the North Carolina Department of Health and Human Services, and Mecklenburg County and Randolph County Public Health), "COVID-19 Contact Tracing in Two Counties — North Carolina, June–July 2020," MMWR, Centers for Disease Control and Prevention; a work of the United States government in the public domain. The report's summary gives 48% of Randolph County contacts as not reached; its results show 47% lost to follow-up and 48% reached, which this page follows.