How to Think About Personal Risk When COVID Case Data Can’t Be Trusted

The numbers do still have some use, even if they’re less illuminating than before.

Illustration of a person walking across a bar graph like a tightrope.
Paul Spella / The Atlantic

Coronavirus cases are up more than 25 percent in the United States over the past two weeks—and those are just the ones we know about. Experts warn that the true size of the current outbreak could be 10, or even 14, times worse than the official counts suggest.

Take Hawaii, for example. Last week, the state reported about 900 new cases a day, but a spokesperson for Hawaii’s department of health, Brooks Baehr, warned that the true number could be “five, six, seven times” greater. “That would be an extra 4,500 to 6,500 new cases every day,” Baehr told the local news channel KHON2.

What exactly is the average person supposed to do with that information? Many people know that COVID cases—as shown in all those jagged charts and splotchy, color-coded maps that decorate front pages—are likely underreported right now. That uncertainty makes calculating one’s own risk extra tricky. If cases could be 10 times worse than what you see on a graph, how do you know if your local outbreak is bad enough that it’s worth slapping your mask back on? Or, more drastically, canceling plans altogether?

All of this uncertainty could be a bargain worth taking. Washington Secretary of Health Umair A. Shah told me that his state’s COVID team anticipated this data gap cropping up with the distribution of at-home tests, which aren’t always included in official tallies. But for Shah, giving people the tools to swab themselves outweighed concerns about losing track of the data. “If I’m going to try to trade off, what’s better? For me to know all the numbers or for me to have people empowered to make good decisions? I would trade off to make sure people are empowered to make good decisions.”

The gap between reported and actual cases is “probably as much of an undercount as we’ve ever had during the pandemic,” Jason Salemi, an associate epidemiology professor at the University of South Florida College of Public Health, told me. The state of Washington doesn’t attempt to predict the gap between real and reported cases, Shah told me. “We feel that whatever [estimate] we come up with is likely not going to be accurate. Because when you don’t know, you don’t know, right?”

Salemi cited three big reasons for the size of the fissure this spring: first, the increased availability of at-home tests; second, a decline in testing overall; and third, the mix of viral conditions—or the fact that variants thought to cause less-severe disease are circulating around a country that’s already got a good amount of immunity thanks to vaccination and infection. The last combo can lead to fewer people coming down with symptoms, which may make them less likely to get tested, he said.

At-home tests offer a kind of pandemic-tracking catch-22. While such tests have afforded Americans more visibility into their own dance with the virus, they also make measuring the pandemic’s movement from afar challenging: A positive result in one’s living room doesn’t always work its way into the official count. (The CDC does not require such results to be reported, but “strongly encourages” that people let their health-care provider know. Some test makers, states, and counties offer options for self-reporting one’s results.) “In a perfect world, obviously, we need to figure out ways to make sure that these at-home antigen tests, those results are making their way into the official numbers,” Salemi told me. “But it is way more important that people are taking advantage of the at-home antigen tests and utilizing them to make decisions in how to interact with their community.”

So should Americans just throw out case-level data entirely? Experts told me that the numbers do still have some use, even if they’re less illuminating than before: monitoring the direction of the pandemic—particularly if used in combination with other metrics that aren’t affected by testing volume or the popularity of at-home tests.

They pointed me toward several alternatives, including hospitalizations, the number of people on ventilators, the number of patients in the ICU, deaths, and wastewater data, as well as keeping tabs on what variants are circulating. “If I had a cockpit with all those gauges, I would look at all that,” Shah told me, though he stressed that he’d prefer that members of the community focus more on taking action than on data—that is, masking up and getting boosters over refreshing charts.

If you are frequently monitoring the data, maybe consider your cadence. I asked Salemi if people who are very worried about COVID should really be checking four or five pandemic metrics daily. “I think you’re doing yourself a big disservice if you’re looking at these numbers every single day, because there are reporting anomalies and things that change,” he said.

Tara Kirk Sell, of the Johns Hopkins Center for Health Security, said that she’s personally watching COVID case numbers “mostly to understand trends” and assumes they’re undercounted. “I don’t worry too much that I don’t know exactly what the level is since ‘a lot more people are getting sick right now’ is close enough for personal decision making,” she told me over email.

Elizabeth Carlton, an associate professor at the Colorado School of Public Health, suggests starting with the CDC’s community-levels map, which assigns counties colors using a combination of three metrics (one of which is cases). Green is low, yellow is medium, and red is high. If your county is in the red, then “no more data-sleuthing needed,”she wrote in an email—start wearing a mask indoors. If it’s yellow, “a simple approach is to round up.” As for green: “Personally, I have been treating green as low-risk and, in that case, rarely wear masks in public unless it’s really crowded. That said, I don’t have an immune-compromised household member and at least one person in my household already had a SARS-CoV-2 infection.”

Another option would be to forgo charts overall, and mine your social network for clues. “If you’re hearing your friends and your co-workers get sick, that means your risk is up and that means you probably need to be testing and masking,” Samuel Scarpino, the vice president of pathogen surveillance at the Rockefeller Foundation’s Pandemic Prevention Institute, told The New York Times earlier this year.

And of course, you can always put to use the very thing that’s contributing to the chaos: Just last week, the Biden administration made a third round of free at-home tests available to Americans. While they may not sharpen our collective understanding of the pandemic, they can at least provide individuals with a bit of control—something that’s been hard to come by amid two years of upheaval.