Recent CDC study in Mecklenburg, Randolph counties, showed difficulties in effective contact tracing
North Carolina doesn’t make the details of contact tracing efforts public as some other states do. But the televised pleas by the state’s leading health official for people to answer contact tracers’ calls offer a clue to the obstacles.
In fact, the Centers for Disease Control and Prevention conducted a study this summer of contact tracing in Mecklenburg and Randolph counties and found significant public resistance to the long-established health practice of finding people who have come into close contact with someone who is infected with a contagious disease.
Contact tracing is a strategy, along with testing and quarantining, intended to help contain the virus. But now that the viral spread is uncontrolled, tracing in North Carolina and the nation is “extremely difficult,” according to the website COVID exit strategy, published by public health and crisis experts, including several from Duke University.
RTI epidemiologist Pia MacDonald says contact tracing is still important. Even with coronavirus vaccines on the horizon, the virus will continue to circulate and contact tracing will be critical, she said in an interview this week. “Regardless of how hard it is to do it perfectly now, it’s still worth trying to do it,” MacDonald said.
Not everyone is going to be vaccinated right away, she said, and some people will never take a vaccine.
“Even though we have a vaccine, it’s not going to be the magic bullet,” she said. “It’s not going to bring an outbreak down to zero.
“If one case is identified, you need to go in and mitigate it before it can amplify again. It’s one of those tools we need in public health. We need to get better at it, and we need to use it for future threats.”
Traditional contact tracing is a labor-intensive practice in which trained interviewers call people who have tested positive for the coronavirus to find out where they’ve been and who they may have infected. Contact tracers then call those close contacts. The CDC advises people who were in close contact with an infected person to stay home and away from others for 14 days.
In Mecklenburg County 48% of people with COVID-19 told contact tracers they had no contacts, and 25% of the names they did pass on to interviewers could not be reached, according to the CDC report. In Randolph County, 35% of people who tested positive reported no contacts and 48% of their contacts could not be reached.
The proportions of people in Mecklenburg and Randolph who said they were not in close contact with anyone were high compared to responses to infectious disease tracing before the coronavirus pandemic. The results in the two North Carolina counties were similar to those in Maryland and New Jersey, the report said.
“Despite aggressive efforts by health department staff members to perform case investigations and contact tracing, many persons with COVID-19 did not report contacts, and many contacts were not reached,” the study says. “These findings indicate that improved timeliness of contact tracing, community engagement, and increased use of community-wide mitigation are needed to interrupt SARS-CoV-2 transmission.”
The study looked at contact tracing results in Mecklenburg for June, and from June 15-July 12 in Randolph. In June, 7,116 Mecklenburg residents tested positive for the coronavirus. Over the last 14 days of this month, the county has added 3,776 cases, according to the state Department of Health and Human Services.
Randolph had 589 COVID-19 cases over the four weeks in June and July that were the focus of the CDC study. During the last 14 days, Randolph has added 667 cases, according to DHHS.
In an email last week, Randolph County Health Director Susan Hayes said people remain reluctant to identify their close contacts.
“We find that cases are more likely to tell us who their family contacts are, but no one beyond that inner circle,” she wrote.
Mecklenburg County Health Director Gibbie Harris said last week that contact tracers try to contact everyone who tests positive within 24 hours and notify the people they’d come close to within 24 hours of the interview.
But they may have to change their strategy as the caseload grows, Harris said in an email last week.
“A significant or sustained increase in COVID-19 cases may adversely impact our ability to reach cases and/or contacts within that timeframe, which results in decreased effectiveness of these interventions,” Harris wrote. “During times of high caseloads, it may be necessary to prioritize case investigation and contact notification with a focus on high risk cases and contacts.”
Brittany Baker, a clinical assistant professor at NC Central University, has done some contact tracing as part of a clinical practice separate from her job at the university. A conversational approach works best in the calls, Baker said in an interview.
“I ask where they’ve spent their time in the days prior to their positive test,” she said. “That yields a little more information.”
Testing positive for the coronavirus carries a stigma for some people, Baker said, and some of those she’s spoken to fear people around them being notified, even though interviewers don’t name the person who tested positive in conversations with their close contacts.
It would help to train more people who have established relationships in a community to do the interviews, Baker said. “They have mutual trust,” she said. “It’s like speaking to someone you already know.”
A Pew Research survey published Oct. 30 found that while most people would be at least somewhat willing to talk to a public health official about the coronavirus, 41% would not.
The survey found partisan differences in how people would respond to contact tracing, identifying contacts and quarantining. Six in 10 Democrats said they would be comfortable with each of these steps, Pew reported, compared to just 36% of Republicans.
The state’s COVID-19 app is meant to get around people’s reluctance to identify their close contacts, Emily Sickbert-Bennett, an epidemiologist at UNC Medical Center, said in an email. The app anonymously identifies people’s contacts who self-report that they’ve tested positive.
Contact tracing was an “extremely effective strategy” in controlling diseases such as Ebola and smallpox, Sickbert-Bennett wrote. But increasing COVID-19 cases make the traditional methods of calls and interviews more difficult.
The SlowCOVIDNC app the state launched on Sept. 22 notifies people when they’ve been exposed to those who tested positive for the coronavirus. Its accuracy depends on people downloading the app and using it to report positive test results.
People notified that they’ve been around someone who tested positive don’t know who that person is, and the person with the positive test doesn’t know who gets notified, according to DHHS.
DHHS spokeswoman Kelly Haight Connor said in an email last week that as of the morning of Nov. 10, the app had been downloaded more than 348,900 times, 113 people had input notification of a positive test result, and the app had sent 816 exposure notifications.
A study by Oxford University and Google concluded that tracing apps, combined with traditional contact tracing, reduces hospitalizations and deaths even when only a relative few use them.
DHHS does not have a hard target for app downloads, Connor’s email said. Promotion was focused initially on colleges and universities, she wrote, but that is expanding.
More contact tracers will be hired to join the more than 2,400 full and part-time people working on that effort in local health departments, the email said. “Contact tracers in North Carolina have investigated thousands of cases to identify possible exposures to help individuals get tested, stay isolated and get the resources and services they needed, and they continue to investigate the increasing number of cases.”
MacDonald, the RTI epidemiologist, said extensive public education about contact tracing is needed to get people to understand what it is and be willing to talk to public health workers.
“There’s a lot of prep work that needs to happen before you just make the call,” she said.
Hayes, the Randolph County health director, said contact tracing efforts need to continue despite the challenges.
“What everyone needs to understand is that controlling coronavirus is not dependent on one strategy, but multiple mitigation strategies,” she wrote. “Layer upon layer, one on top of the other, including social distancing, masks, hand hygiene, isolation, quarantine, and ultimately vaccines.”