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Minnesota is contacting people who have been exposed to COVID-19 cases. At current infection rates, it might not do much good

The state has hundreds of workers making calls to people who test positive for COVID-19, and with those they may have been in contact with. But with high levels of community spread of the disease, those efforts have limited benefits.

test for the coronavirus
The number of daily new cases in Minnesota is so high that contact tracing will be of little use in containing the epidemic.
REUTERS/Sergio Flores

If you test positive for COVID-19 in Minnesota, you’re going to get a phone call from a public health worker who wants to know who you are, where you likely picked up the virus and whom you might have spread it to.

These efforts to test, trace and isolate COVID-19 cases have been ongoing since the start of the pandemic, in which time the number of people making the calls has increased from about 20 to hundreds.

The good news is that the Minnesota Department of Health (MDH) thinks it now has enough contact tracers to handle the state’s current caseload. The bad: The number of daily new cases in Minnesota is so high that contact tracing may be of little use in containing the epidemic.

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Test, trace, isolate

Contact tracing is nothing new — it’s used routinely to intervene in measles, whooping cough and other outbreaks. But unlike those diseases, which vaccines and antibiotics fend off, there isn’t a cure for COVID yet. All public health officials can do in this case is recommend to those who have been exposed to the novel coronavirus to distance themselves from others.

“We have to rely on the non-pharmaceutical stuff. It’s a little bit like turning back the clock to 1918,” said Kathy Como-Sabetti, an MDH epidemiologist, referring to the flu epidemic.

The current contact tracing strategy revolves around phone calls. “We call people, we do an interview, we ask for their contacts, we call their contacts,” Como-Sabetti said.

So when someone tests positive, they can expect to get a phone call from a contact tracer asking them information about demographics like age, race and ethnicity, where they live, what their living situation looks like and where they might have acquired the virus.

“Have you been out and about? Have you been to bars and restaurants, doing sports, whatever it may be,” Como-Sabetti said.

When a tracer gets a case, they call, and leave a voicemail if the person doesn’t pick up, asking them to return the call. Refusal rates are pretty low — around 3 percent, Como-Sabetti said.

Tracers also ask about a person’s contacts. Going back 48 hours before the person developed symptoms, or 48 hours before they were tested for those who are asymptomatic, the contact tracer determines whom the positive case was at risk of exposing to coronavirus.

Oftentimes, the main people exposed to a positive case are the people who live with them, and those household contacts are already aware that their family member or roommate has COVID-19.

But additional calls are made to others who may have been at risk of exposure. That typically includes anyone who was within 6 feet of a person for at least 15 minutes. But it obviously ranges — kissing someone for 30 seconds is a more intimate, though shorter form of contact that could also transmit the virus.

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Tracers consider social contacts and workplace contacts. In some employment situations, such as if someone works at a child-care facility, public health officials coordinate with the employer to help determine who was exposed and how to best notify people.

The situation gets trickier in some social settings — like bars, which have been catalysts for outbreaks in the last month-or-so.

“There really isn’t a good way to get ahold of every person who came to a bar,” Como-Sabetti said. “For that reason, we have been providing bar and restaurant names when we have evidence of transmission and they meet a certain threshold that we feel comfortable.”

In the last month, for example, MDH has announced outbreaks stemming from bars including Cowboy Jack’s and the Kollege Klub in Minneapaolis and Rounders Sports Bar and 507 in the Mankato area.

People who are deemed at risk of possible exposure to COVID-19 are asked to stay home and quarantine for 14 days after their last exposure to the positive case.

The Kollege Klub in Dinkytown
MinnPost photo by Peter Callaghan
The Kollege Klub in Dinkytown was implicated as a source of a recent outbreak of the coronavirus.

Enough tracers?

When the pandemic started, MDH had about 20 workers doing contact tracing. Today, between Minnesota Department of Health and local public health officials, plus a contractor with workers available to provide surge staffing, there are currently a potential 800 people making contact tracing phone calls in Minnesota.

How many contact tracers are needed to adequately manage a pandemic depends on whom you ask, and what the spread of COVID-19 looks like at any given time. A staffing calculator by researchers at George Washington University suggests a baseline of 15 tracers per 100,000 population, which suggests Minnesota would need about 882. But it also has a staffing output that takes into account current case loads and suggests Minnesota needs more than 3,000 contact tracers.

A mid-June report by National Public Radio found that only 14 states had the staffing levels or had reserve staff adequate to meet their state’s needs based on case counts, using the GW metrics. Minnesota wasn’t one of them.

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The current staff in Minnesota has been enough to handle caseloads, Como-Sabetti said — MDH has reported between about 500 and 862 new cases daily in recent days —  but MDH is planning for a potential worst-case scenario where cases rise in the fall, leading to a doubling or tripling of current staff levels. Como-Sabetti said MDH will likely make a proposal to the state for funds to reach those levels.

The department is also looking to add technology that would streamline the process for people who don’t need as much guidance, including texting people or having part of their interviews done as a survey online.

“Some people need more help and they need more information than others. We’re trying to accommodate people who need a lower level of intervention,” she said.

Does it even matter?

While contact tracing is one of the only tools to manage a pandemic that has no real pharmaceutical preventions or cures, it is not always very effective as a containment strategy.

Contact tracing as a means of preventing a virus’ spread works best when there isn’t a lot of transmission of the virus in the community. That’s because when there are few infections, it’s easier to test, trace and isolate the people who have them and any potential contacts.

That’s part of what makes it so important to get the number of cases down. It actually becomes feasible to test, trace and isolate a large share of the cases when there are fewer of them, said Michael Osterholm, the director of the Center for Infectious Disease Research and Policy at the University of Minnesota.

Osterholm listed Hong Kong, Singapore and some European countries as places where caseloads have been successfully reduced enough to effectively test, trace and isolate. But examples of places that have been successful aren’t just abroad.

“One of the things I think the state of New York has demonstrated is when you do not just bend the curve but drive the case numbers down, you can do test and trace,” he said.

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Here in Minnesota, case counts have been on an increasing trajectory since mid-June. On Sunday, MDH reported a record 862 new cases and about a third of the cases have no known source of transmission.

“The numbers here are just way too high,” Osterholm said. “What we should be striving for is to see — if we get our numbers to one-tenth of what they are today, then we have a real chance of doing contact tracing and follow up. If not, it’s going to be a challenge.”

Michael Osterholm
University of Minnesota
Michael Osterholm: “One of the things I think the state of New York has demonstrated is when you do not just bend the curve but drive the case numbers down, you can do test and trace.”
Another problem for U.S. contact tracing efforts is the time it’s taking to get test results back. With a surge in cases around the U.S., test results are taking longer to come back than they previously had — sometimes a week or more, at which point a person who tested positive may not be infectious any longer.

This complicates contact tracing. While people are asked to remain at home to limit exposure as they wait for test results, COVID-19 is thought to be most infectious before people who develop symptoms get them, which means exposure can occur before anyone suspects it.

“Contact tracing is limited in what it can do when there is widespread transmission given both the issue of the impact that asymptomatic transmission has on overall transmission as well as just the sheer numbers and the timeliness of testing, how fast can you get test results back,” Osterholm said.