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Contact tracing in Illinois may not slow the coronavirus much. But the data is helping guide state decisions.

Chicago Tribune - 11/25/2020

Since the start of the pandemic, Dr. John Schneider has interviewed more than 100 people with COVID-19, and in nearly all cases he managed to pin down how they got infected.

“I think there’s one person I’ve had who said, ‘I don’t know how I got it,’” said Schneider, an infectious disease specialist affiliated with the University of Chicago who is director of the 55th Street Howard Brown Clinic, where he also does case investigations and contact tracing. Schneider says the man did visit a barber shop, so they are checking to see if that might be the source.

“But everyone else is like, ‘Oh yeah, so-and-so and so-and-so is sick now too.’ Or ‘so-and-so got tested and they were positive too,’” Schneider continued. “They all know how they got it. They got it from someone in their friendship, or in their household network, who got it from work or some other mechanism.”

Contact tracing for COVID-19 has gotten off to a slow start in Illinois, with the state still short of its initial goal of 3,800 people doing that work. And now, with infections soaring, caseloads are overwhelming tracers’ ability to slow the spread of the virus by tracking down contacts and getting them to quarantine.

But the information gleaned by Schneider and other contact tracers is proving useful in another way: It is feeding a growing database that Gov. J.B. Pritzker has cited as a guide in making decisions about pandemic restrictions. The governor singled out the data, along with scholarly studies, when defending his late October decision to shut down indoor dining.

Experts on contact tracing say that using contact tracing data in this way is valid and part of the reason contact tracing is done in the first place, particularly when cases are surging.

When case levels are higher, “understanding where people have gotten infected is going to help us understand what are the risky places or risky activities that can inform what kind of response we want to do,” said Jaline Gerardin, assistant professor of preventive medicine at McCormick School of Engineering at Northwestern University.

There are limitations. Sometimes, despite Schneider’s experience on the South Side, it’s hard to pin down where and how a person was infected, making it difficult to identify outbreaks. Tracers also gather information on places visited by infected people -- so-called exposure data -- but whether those places are truly unsafe can be a matter of interpretation.

And in Illinois, the data is far from complete, both because the state’s system for tracking the data is still developing and because some populous areas of the state aren’t even close to conducting contact tracing on every case.

For example, the state is getting only rudimentary contact-tracing information from Schneider’s work at Howard Brown at this point because of the limitations of Chicago’s own database, Schneider said. The city and state databases are not collecting all the same information and aren’t yet fully communicating, officials confirmed.

Across Illinois, less than half of people with COVID-19 diagnoses were interviewed by case investigators from Aug. 1 to Nov. 14, according to state data. The lowest interview rates were in Chicago, which was at 18%, and Cook County, with only 12% of infected people interviewed.

Crystal Watson, a contact tracing expert who’s a senior scholar at the Johns Hopkins Center for Health Security, said that although “the data is not going to be perfect” amid a case surge, it’s still useful in informing government decisions.

“I think contact tracing and case investigation are really important in understanding where people are getting the virus,” Watson said. “Where there are clusters of cases (or) large transmission events (that can help) inform decisions by public health agencies about where to allocate resources and what policies to put in place to reduce transmission.”

The data so far

The state first posted some contact tracing data on Nov. 6, showing what percentage of infected people case investigators tried to reach and the percentage they actually did reach, broken down by regions of the state and also its 97 public health departments. The information, kept by the Illinois Department of Public Health, is updated each Friday.

In all, case investigators -- the workers who reach out to infected people in the first step of the contact tracing process -- tried to contact 58% of the 383,709 people who contracted COVID-19 between Aug. 1 and Nov. 14. They actually talked to 45% of them.

The data also shows that contact tracers reached out to 73% of the 268,572 people who were identified through case investigation as having prolonged, close contact with infected people. In the end, they talked to 62% of the contacts, the data indicates.

The posted data includes information on outbreak locations, or places at which five or more infected people from different households had been within a 14-day period. Those cases cannot be linked to another source of infection.

The top five outbreak locations since July 1 -- when Pritzker lifted many early pandemic restrictions -- were factories, group homes, community events, correctional facilities and colleges. In the past 30 days, the top five were group homes, child day cares, factories, correctional facilities and retail locations. The specific locations are not identified.

Also listed are potential exposure locations, or places infected people said they were in the 14 days before experiencing symptoms or receiving positive test results. That data includes this caveat: “Locations provided by cases should be interpreted as locations where COVID-19 exposure may have occurred, not that these are definitive exposure or outbreak locations.”

The top exposure location in the 30 days ending Nov. 13 was schools, followed by hospitals and clinics, business and retail locations, restaurants and bars and “other,” which includes travel and vacations.

The state also posted separate data from Chicago showing that, of 1,090 infected people interviewed in the city who said they had been to public places in the 14 days before symptoms or a positive test, more than half reported visiting restaurants and more than 1 in 10 said they went to a bar, based on interviews conducted between July 15 and Sept. 15.

Other data posted includes school outbreaks, or specific schools that reported five or more cases from different households “who may have shared exposure on school grounds” -- whether during class hours or before- and after-school activities -- during the previous 30 days. As of Nov. 13, it identified 15 school districts with outbreaks among students, staff or both.

And finally, the data also lists 730 schools outside the Chicago Public Schools system where potential exposures occurred in the 30 days before Nov. 13. The most recent data, for the week ending July 11, listed more than 1,500 exposures at schools, broken down by age group, with the bulk of cases in students ages 18 to 22.

Separate data from Chicago Public Schools, meanwhile, shows case numbers among adults going to CPS locations soared in the month before Nov. 14.

Setting restrictions

When Pritzker announced the release of the data on Nov. 6, he was under some political fire for shutting down indoor dining a week earlier. Restaurant owners struggling to save their businesses from COVID-19-related financial collapse said the data didn’t prove restaurants were dangerous.

The most recent data, on tracing conducted since July 1, ranks bars ninth on the list of outbreak locations with 24 counted, while restaurants are 11th on the list with 22 outbreaks listed. By comparison, factories and manufacturers were at the top of the list, with 69 locations across the state reporting outbreaks.

During the 30 days ending Nov. 13, bars were 15th on the list, with two outbreaks, and bars were 19th, with one outbreak. At the top were group homes, with 16.

But restaurants and bars, categorized together, were fourth on the latest list of exposure locations, based on data for the 30 days ending Nov. 13. There were 2,107 potential exposures identified at bars and restaurants, behind schools with 3,718 potential exposures; hospitals and clinics with 2,384; and retail locations with 2,290.

Pritzker discussed bars and restaurants when announcing the new database, making a case that the exposure data was a better guide than outbreak data for these businesses.

He cited bars and restaurants as the biggest location for exposures other than the catchall category of “other,” which included things like vacations, family gatherings, weddings and college parties. The period of time he cited covered Aug. 1 through Sept. 29, not the most recent available statistics.

“The location of an outbreak is more difficult to identify than the location of an exposure,” Pritzker said. “While certain settings like a college campus, a factory or a group home may make it easier to determine an outbreak, most establishments that are frequented by the public like restaurants or grocery stores are not easily determined as the setting of an outbreak.

“Much more useful for identifying regular locations that amplify the spread of the virus is exposure data,” Pritzker added. “Exposure data is going to give you a sense of where you’re at the greatest risk for catching COVID-19 and particularly when we see community transmission as high as it is around the state.”

He also noted the high count of exposures at restaurants and bars and cited a Centers for Disease Control and Prevention study that showed people infected with coronavirus were about twice as likely to have dined at a restaurant in the two weeks before diagnosis than those who were not infected with the virus. And he noted that eating at a restaurant required removing one’s mask while being in a place with others for extended periods of time.

But the restaurant industry disputes Pritzker’s conclusion, underscoring that relatively few outbreaks have been linked to restaurants and that exposures don’t necessarily mean the identified location is the source of virus transmission.

Sam Toia, president of the Illinois Restaurant Association, also noted that factories are higher on the exposure list but weren’t shut down. And he maintained that stopping indoor dining with strict COVID-19 protocols would only push people into unregulated private gatherings where people would be less safe.

“We know how to do this right: social distancing, wearing your mask, diners in seats, possibly curfew, nobody standing, nobody standing behind bars,” Toia said. “We get all that.”

He maintained that lowering capacities, as suggested in a study by Northwestern and Stanford universities that was published in the journal Nature, would tamp down disease spread while allowing businesses to keep their heads above water.

Schneider, the physician and contact tracer, said he is skeptical that diners are being infected at restaurants by workers or by other people they don’t know, even though scientists suspect infectious aerosols could linger in enclosed spaces. It’s more likely, he said -- and in keeping with what he has gleaned from interviews -- that people are getting the virus from their own dining companions.

“Someone in their group has it, or had it, and was asymptomatic and didn’t know,” Schneider said. “People are going to restaurants with friends, or their extended families, or people they haven’t seen, and someone was infected. I think that’s pretty clear.”

But he said he also has interviewed restaurant staff who appear to have contracted the disease at work, which he suspects is the result of working in bustling spaces like kitchens.

Nevertheless, Schneider was not critical of Pritzker for taking “a conservative approach” by stopping indoor dining.

“These are difficult decisions that policymakers have to make -- I get it,” he said. “I think at the current rates we’re seeing right now, I definitely get it. ... Now it kind of makes sense to try to limit any activities because of the way cases are going. But can we pin this on restaurants? I would say no.”

Northwestern University’s Gerardin, who was one of the authors of the Nature study on limiting capacities, said the number of exposures found at restaurants is “a warning. ... The contact tracing is giving you red flags that are telling you where to look, and then you should follow up to figure out is it truly a risky place or just a coincidence? What is going on?”

Watson, at Johns Hopkins, said Pritzker’s decision was warranted.

“In addition to the data they are looking at in Illinois, we have lots of other evidence from other states, other countries, to corroborate that indoor dining and bars and gyms ... are the kinds of environments where transmission happens much more readily,” Watson said. “And so I completely agree with the policy decision to shut down those locations, especially in the midst of a very severe surge of cases.”

What about schools?

Although Pritzker pointed to exposure data, along with the CDC study, to defend his shutdown of indoor dining, he downplayed the relatively large number of potential exposures related to schools.

“Anyone who goes into a school building regularly would have likely reported school as a place they went before they became a confirmed positive,” Pritzker said. “That doesn’t at all mean that school is where they contracted the disease originally, and remember that masks are required in school and are not intended to be removed for extended periods of time.”

Jordan Abudayyeh, Pritzker’s press secretary, said in response to Tribune questions that Pritzker’s decisions are guided by both contact tracing data and scientific studies. Indeed, when Pritzker made his announcement, he also cited research on the efficacy of face masks, good ventilation and physical distancing.

“Schools are environments where masking and distancing guidelines are enforced compared to other indoor activities where the motive isn’t educating students safely, but instead profit,” Abudayyeh said in an email. “I’d also note that we only have about 169,000 students in full in-person instruction. As positivity rates around the state grew, school districts have amended their learning plans to keep students and teachers safe.”

Decisions about whether to keep schools open, like those surrounding restaurants, are some of the most controversial the governor must make. In many areas of the state, parent coalitions are fighting to keep schools open or open them up, while many teachers unions contend it’s safer to conduct remote learning.

School opening and closing decisions also are fraught with other considerations. Some educators say students not equipped for remote learning could be falling further behind.

Watson said disease can spread at schools, but added that deciding whether to keep them open should be a much higher priority than making a call about bars.

“That’s a decision that has to be made by the leaders,” she added. “I don’t think schools are exempt from clusters of transmission, but it is a priority decision.”

hdardick@chicagotribune.com

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