On any given day, the Shelby County Health Department cannot reach 15% to 20% of the positive cases on its list for contact tracing.

So, if 100 new positive cases are reported one day, that’s 15 or more people whose close contacts are not identified and could be actively spreading the disease.

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The health department does not publicly report the percentage of calls it completes in 24 or 48 hours, or the percentage of people it could not reach.

“To know that I’m reaching easily 70%, and maybe at best, 85% of the people we’re trying to reach, but we don’t reach the rest, at the end of the day, how much does that change your life?” said David Sweat, deputy director of the Shelby County Health Department.

“What extra steps are you going to take to protect yourself or another person by knowing that, versus what you didn’t know?”

While he says the health department will consider posting the data, the bigger issue, he says, is that anywhere from 15% to 30% of the people it is trying to reach are very difficult to find, and 10%-15% are them are never located.

Nationally, COVID-19 metrics that health departments post vary substantially, including data the public could use to evaluate the effectiveness of contact tracing efforts, notes Dr. William Schaffner, professor of preventive medicine and health policy at Vanderbilt University.

“It’s an important public health metric that is certainly important for the director of the health department and board of health to evaluate,” Schaffner said.

“It’s perfectly reasonable to put that on the website, so that the public, particularly the very interested public, has a sense of how they’re functioning. But we have to recognize that it’s not going to be anywhere close to 100%.”

Only a handful states post data showing how efficient their contact tracing is. Late this summer, 14 states were posting contact tracing data to government websites; nine posted data on the number of staff doing contact tracing.

Neither Tennessee nor Shelby County post either metric.

Nationally, the goal is that 75% of people who have tested positive for COVID-19 be contacted within 24 hours, says Marian Levy, associate dean and professor in the University of Memphis School of Public Health.

“If you’re not able to reach 75% in contact tracing, the pandemic will continue to spread,” Levy said.

While she doesn’t expect the Shelby County Health Department to post the exact figures of the contacts it reaches, “the public needs to be aware of the fact that’s very important to be able to trace people who’ve been exposed to COVID-19.”

Sweat says the health department reaches 70% of the people who have tested positive within 48 hours, and another 10%-15% in some interval of time after that.

There is no metric on the website or place people can go to see the data, including how it changes as case numbers rise or fall.

In July and August, when the number of daily positive cases was 500 to 600, the department had an accumulated backlog of several thousand cases in which people were never called for contact tracing.

On Sept. 30, Sweat said all the cases had been assigned to a tracer.

“There are some cases that we have not reached. We are still trying to reach them,” he said. “We’ve sent letters and we’re trying to see if they will call us back so it can finally be closed down.”

There is not a way to verify how many of those interviews have been completed or are still in process.

In the trenches

Contact tracing is done in a race to quell the spread of infection, ideally within the first 24 hours of diagnosis.

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The person who has tested positive is asked to identify every person with whom they were within 6 feet of for 15 minutes. Each of those people is then contacted and asked to quarantine.

Every case identified and put in isolation presumably stops the infection from being passed on to another.

Over the summer, the health department was doing the work with staff borrowed from other places in the department.

This summer, it hired 45 tracers with federal CARES Act funding, which expires Dec. 31.

Another 70 will start over the first two weeks of October, when the health department will be running two shifts of tracers.

Four teams of tracers now are rotating in and out of the office on Dividend Drive seven days a week.

“A good interview will take a half hour,” says Tijuana Jefferson, one of the tracers hired in July.

Most days, she says can do four or five strong interviews. But if people are reluctant to give information, “that 30-minute conversation may be cut to 10 minutes.”

Under that timeframe, the current staff can do 225 solid interviews a day.

Sweat says they are easily doing more.

“It may be a shorter interview, but we will get most of what we need,” he said.

With daily cases into the first week of October hovering around 100, “it’s well within their capability at the moment.”

Tracers make about $20 an hour, Sweat said. Those hired this summer and fall were all hired with the understanding that funding currently exists until the end of the year, although he says there are multiple possibilities for other funding sources, “including we get to rollover unspent funds or continue to work for as long as the money lasts or Congress puts more money into the program.”

The uncertain funding has an effect on staff retention because some, Sweat says, have taken the jobs until something better came up.

“They’re grateful for the employment and the opportunity to help, but being rational economic citizens, they’re also not necessarily stopping their job search for a more permanent position.”

Others find they are not suited to the work, which Jefferson described as requiring empathy and patience. In other cases, they may have a skill the health department needs in another area and are offered that post.

“But then, that leaves us with a vacancy,” Sweat said. The turnover rate runs 7-8%, he said.

The work is done in a warren of cubicles with a desk, chair, phone and laptop.

“I do my best to let my voice be my in-person over the phone,” Jefferson said. “I try to gauge their tone and let them know that ‘I may not understand exactly what you are going through, but I understand that we all are dealing with this though.’

“I wouldn’t say it’s a dead end because sometimes we are their initial contact. So, if they don’t give me their whereabouts, I’m still able to inform them, ‘Hey, are you aware of your results? These are the safety measures you need to take,’” she said.

“We’re still making progress by letting them know that they are infected, and this is what they need to do, so that does prevent the spread in a sense.”

The search

According to Levy, 36% of contacts don’t have an accurate phone number, and nationally, tracers are able to reach only 20% of the names on their contact lists.

“So, unless you do a lot of digging, have accurate numbers and people to follow up, you’re not going to be very successful,” she said.

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Tracers in Shelby County follow a variety of leads, Sweat said.

“If we have record of the person coming to the health department for a different reason, we’ll try that contact info. We do Facebook searchers. We do social media searches. There’s a number of things we do before we give up.”

In this day, with caller ID info, people can see who is calling, said Schaffner.

“These calls can be invasive and they may not want to tell you what their whole life has been like, who they’ve been with for the last two weeks,” he said. “They know what the reason for the call is.”

For that reason, he says, contact tracing alone is imperfect for reducing transmission.

“All of the tools we use in public health have utility. And they all have gaps,” Schaffner said.

But combined with masks, hand washing and social distancing, they create a safety net that has worked in other pandemics.

The Shelby County Health Department is several weeks into an enhanced data collection process that director Alisa Haushalter has said will give it a “laser-like focus” in determining where transmission is happening.

With additional staff the department hired this fall and the extra datasets, the health department last week determined it was safe to reopen bars.

“We added fields to the social gathering section,” said Umar Kabir, an epidemiologist in the Shelby County Health Department. “We captured questions that dig down and find out where you’ve been — the category or places where you’ve been; when you’ve been to those places and where those places are located.”

A test case is the University of Memphis, which has 36 active cases — six of them contracted on campus. It also has 80 people who have been exposed and are being monitored, according to data it posted on its website on Sept. 30.

“The payoff is coming,” Sweat said. “But the big effort was to figure out the questions. We had to sit down and say, ‘What do we wish we knew that this tool is not helping us find out?’ ”