The ubiquity of at-home testing could make the next COVID-19 wave "invisible"

More people may have COVID than official counts suggest. But there's an easy way to figure out if there's a surge

By Nicole Karlis

Published April 12, 2022 5:41PM (EDT)

A Walmart worker shows she tested negative after using one of the new government-issued COVID-19 Antigen Rapid test kits she received to take a self-test while at home on February 8, 2022 in Provo, Utah. The test kits are arriving as COVID positive test results are starting to fall in many states. (George Frey/Getty Images)
A Walmart worker shows she tested negative after using one of the new government-issued COVID-19 Antigen Rapid test kits she received to take a self-test while at home on February 8, 2022 in Provo, Utah. The test kits are arriving as COVID positive test results are starting to fall in many states. (George Frey/Getty Images)

On Monday, Philadelphia announced that it would be the first major U.S. city to reinstate its indoor mask mandate. Public health officials say they're concerned by a sharp increase in COVDI-19 cases in the city — over the last 10 days, cases have spiked by 50 percent.

"If we fail to act now, knowing that every previous wave of infections has been followed by a wave of hospitalizations, and then a wave of deaths, it will be too late for many of our residents," said Dr. Cheryl Bettigole, the city's health commissioner. "This is our chance to get ahead of the pandemic, to put our masks on until we have more information about the severity of this new variant."

However, the news comes at a time when overall cases across the country continue to drop or remain somewhat static, according to data from the Centers for Disease Control and Prevention (CDC), despite mixed predictions that BA.2 — the highly transmissible BA.2 subvariant of omicron — will cause another surge in COVID cases in the United States.

But what if that data, unlike previous data from COVID-19 waves, is wrong? That's the prospect posed by this latest COVID wave, and the reason for it is simple: most positive at-home tests don't get officially counted in public health numbers the way clinic-administered tests or COVID-related hospital visits might. 

Hence, while the official increase in cases in Philadelphia amounts to more than 140 cases per day — a fraction of what Philadelphia saw at the height of the omicron surge — some experts who monitor COVID-19 cases across the country are wondering whether at-home tests are affecting accurate data tracking, especially when it comes to knowing whether or not the country is experiencing a BA.2 surge.

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Indeed, the CDC doesn't track the results of at-home tests. Some state health departments, who track their own COVID-19 data, have systems set up for people to report if they have positive at-home tests. But it's unclear how many, if any, do.

While this concern was raised prior to BA.2 at the end of 2021, it had less of an effect in part due to the lack of at-home tests available during the omicron wave. Many of those concerned about symptoms had to take PCR tests if they couldn't find at-home tests. PCR, or polymerase chain reaction tests, require laboratories and special laboratory equipment, but are considered more accurate than at-home tests. PCR test results are also typically reported to state public health agencies, unlike at-home tests.

As Salon reported in January, the shortage of at-home tests were a result of a supply and demand mismatch, and a shortage in testing materials. Since then, the Biden administration has purchased one billion at-home, rapid COVID-19 tests to distribute to Americans for free.

"There's actually going to be a huge tidal wave coming in; we just don't see all of it."

To be clear, the availability of at-home tests is welcome news, as the country faced many previous waves without adequate testing resources. However, as the U.S. faces another contagious variant, the lack of reporting of at-home test results in official counts may create an incomplete picture for local health departments and citizens.

Sara Willette, the founder and Chief Data Officer of Iowa COVID-19 Tracker, said the state of Iowa doesn't include at-home testing in official COVID-19 counts. Willette, who also has an immunodeficiency disorder, has served as something of a community data scientist during the pandemic as she helped track case numbers. Yet she is no longer convinced that official state counts are accurate. 

"The people I know personally — who tested positive at home and never got a PCR mandatory test — were in the counties that we do have wastewater data for, and they tested positive at similar points in time when we saw wastewater data starting to tick up a bit," Willette said. "And that's, at least for me, that's why wastewater data is more reliable."

Willette was referring to the practice of wastewater observation to ascertain how prevalent COVID cases are. In September 2020, the CDC launched the National Wastewater Surveillance System (NWSS) as a means of tracking the presence of SARS-CoV-2, the virus that causes COVID-19, in wastewater samples collected across the country. The CDC says this type of surveillance can stand in as an "early warning that COVID-19 is spreading in a community."

"People infected with SARS-CoV-2 can shed the virus in their feces, even if they don't have symptoms," the CDC states. "The virus can then be detected in wastewater, enabling wastewater surveillance to capture the presence of SARS-CoV-2 shed by people with and without symptoms."

"Wastewater is the most objective, unbiased, politics-free kind of testing . . . and it's clearly showing an increase throughout all regions of the country."

Willette said it isn't a "concern" necessarily that at-home test results aren't included in official public health data counts, but it does imply a "transition in understanding" how COVID-19 is trending. Willette personally prefers looking at local wastewater data as a gauge for figuring out if COVID-19 is spreading in a community.


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Dr. Amesh Adalja, an infectious disease and critical care medicine doctor, told Salon "using wastewater is a more useful tool in the current era," and that "case counts have different meanings than they did pre-home tests."

However, Adalja said "the focus on severe cases is most important, and hospitalization numbers are well suited to that purpose."

Epidemiologist Eric Feigl-Ding, who is also the founder of the World Health Network, told Salon he believes a wave is already underway if one looks at the wastewater data.

"The wastewater doesn't lie; wastewater is the most objective, unbiased, politics-free kind of testing . . . and it's clearly showing an increase throughout all regions of the country," Feigl-Ding said. "And we're also seeing cases rise in many places, too."

Feigl-Ding said that state and federal data counts might not reflect the gravity of case counts due to some states and countries closing their testing sites as well.

"[A wave] is already happening. It is a very unsubtle wave, what we see right now in the next few weeks crashing on the shores is a small, small wave," Feigl-Ding said. "But there's actually going to be a huge tidal wave coming in; we just don't see all of it."

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Nicole Karlis

Nicole Karlis is a senior writer at Salon. Tweet her @nicolekarlis.

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