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If you’re sick this fall, you’ll probably get two virus tests

If you’re sick this fall, you’ll probably get two virus tests


Doctors have to distinguish the flu from COVID-19

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Shortage of corona test capacity in Dutch laboratories
A COVID-19 test.
Photo by Niels Wenstedt/BSR Agency/Getty Images

If you go to see a doctor with flu-like symptoms this flu season, chances are you’re going to get swabbed for two tests: one for the flu, and one for COVID-19. Unlike flu seasons when there isn’t a pandemic, doctors can’t be confident that someone with body aches and a fever has the flu. That’ll change the diagnostic process for both diseases.

“This year, if it looks and smells like flu, it could be flu — or could be COVID-19,” says Richard Webby, an infectious diseases researcher at St. Jude Children’s Research Hospital in Memphis.

Sorting out one from the other is important. The treatment methods may not be that different: someone with a mild case of the flu and someone with a minor case of COVID-19 will both probably be sent home to rest and recover. Knowing someone has COVID-19, though, means they can be told to watch out for signs that the illness is becoming more serious. A COVID-19 diagnosis also triggers public health interventions like contact tracing, so that the virus doesn’t continue to spread.

“We’d like to get rid of them both, but the coronavirus is the one we’re really trying to control,” Webby says. “We want to get that person out of circulation as soon as possible.”

Doctors regularly use rapid flu tests in their offices, with results that come back within 15 minutes, says Anthony Baffoe-Bonnie, the infectious disease chief at Carilion Clinic in Virginia. Flu season hasn’t picked up quite yet, so for now, the first step for treating any patient with respiratory symptoms would be to test them for COVID-19. Once flu tests start coming back positive in his area and when flu surveillance systems start reporting that the virus is circulating, he says he’ll start to add on tests for the flu.

There are a handful of tests available that can check for both influenza and COVID-19 at once: health care companies Roche and Cepheid have Food and Drug Administration authorizations for joint tests, and the Centers for Disease Control and Prevention has one available for public health labs. Those are the best approach, Baffoe-Bonnie says. But they may not be available in every area and at every hospital — most places might have to rely on two separate tests.

Right now, the joint tests are genetic tests: they look for fragments of the influenza genetic sequence and fragments of the coronavirus genetic sequence. Those types of tests require more specialized machinery. The standard, outpatient flu test is usually an antigen test, which looks for the proteins that stick out on the outside of the influenza virus. These tests work fast, and can have results back in about 15 minutes, but tend to be less accurate than genetic tests. Both options are also available for COVID-19 tests.

If a joint test isn’t available, getting tested for both flu and COVID-19 could mean a combination of the testing types. Someone might get a rapid flu test for flu, but a slower, gene-based COVID-19 test. A doctor could decide to send out genetic tests for both viruses to a lab, which could have a turn around time of a few days. People might go to a walk-in COVID-19 testing site for a rapid test, and go to a doctor for a flu test if that comes back negative.

Baffoe-Bonnie says his clinic plans to start with genetic tests for the viruses, while having some ability to do faster antigen tests, if necessary, as well.

All this testing could help get patients better treatment — but it could also be very expensive, worries Edward Belongia, director of the Center for Clinical Epidemiology & Population Health at Marshfield Clinic Research Institute in Wisconsin. Under the CARES act, passed in the United States at the start of the pandemic, COVID-19 tests are supposed to be free for patients. “That’s not true for flu,” he says. In March and April, some people sick with what they thought was COVID-19 were charged thousands of dollars for tests for other respiratory viruses, like flu.

“We don’t want people discouraged from coming in and getting tested because they’re worried about the cost of the laboratory tests,” Belongia says.

That’s a particular worry, because increased testing — and all the costs associated with it — might not be confined to this flu season. There’s still a chance that, even after the pandemic passes, the coronavirus could continue to circulate through the population each year. If that happens, some of the adjustments to the way doctors diagnose the flu could be more permanent, Webby says. Influenza won’t be the only culprit for a feverish, achy patient — they’ll have to consider other viruses, too.

“I think that would put pressure on [the] system to change, not just specifically flu, but the whole respiratory virus testing pipeline,” he says.