Can You Test Positive for Coronavirus and Be at Work? Sports Leagues Say Yes - WSJ

When American sports leagues began to chart their paths for the pandemic, they faced countless questions. How often should they test? Would the NBA’s bubble burst? How many rule changes does it take to drive MLB purists cuckoo?

But the thorniest question they had to reckon with is one that applies to multibillion-dollar sports enterprises and small businesses alike. When is it safe for someone who has tested positive for Covid-19 to return to work?

The answer is as surprising as it is murky. That’s because leagues like the NFL and MLB say it’s safe for players to return even while they’re still testing positive.

Professional sports’ protocols have been under scrutiny since the moment it became clear that sequestered leagues such as the NBA were testing players daily, and delivering their results in hours, as people around the country waited days.

Then came the baseball season. Within five days, half of the Miami Marlins had positive tests and the league began postponing games. Soon after, there was an outbreak on a second team, the St. Louis Cardinals.

Sports leagues already face questions about whether they should play at all during the pandemic. Now they will have to convince America of the validity of protocols that say that players who don’t register a negative test can be back out on the field anyway.

This idea could come into play into when the Marlins try to reinsert players who tested positive into their lineup. It may also play into the NFL season, with players and coaches returning to training camps last week. The positive tests in football have included players and Philadelphia Eagles coach Doug Pederson, who the team said was asymptomatic and in self-quarantine as part of the league’s protocols.

The science behind the protocols has the backing of the Centers for Disease Control and Prevention and independent infectious disease experts. They say that research indicates a person with mild to moderate symptoms of coronavirus will cease to be infectious within 10 days of their symptoms’ onset, and can stop isolating, though in severe cases, it may be more appropriate for them to isolate for up to 20 days.

The CDC has also extended that reasoning to say that an asymptomatic person who tested positive for coronavirus ceases to be infectious 10 days after their test. That’s because some epidemiologists suspect that people could continue to test positive for weeks or even months, but would no longer be infectious.

MLB and the National Football League have taken that finding and run with it.

The easiest way for a baseball player with a positive test to come back is to register two negative results for tests taken 24 hours apart. But if they can’t, there’s a footnote tucked away in MLB’s operations manual that offers them an alternative route: even with repeated positive results on PCR tests, a physician and league medical advisers can review the circumstances and clear the player anyway.

The NFL’s policy says if an individual is positive but asymptomatic, they can return after five days and two negative tests; or they can come back 10 days after the initial positive. If they’re symptomatic, that requires 10 days since symptoms first appeared and at least 72 hours since symptoms last appeared.

Both return protocols also include screening for heart damage, among other exams, and require doctors’ approval. But those are focusing on the positive player’s health—not the team’s.

The idea behind the CDC’s assessment, the linchpin of these leagues’ strategies, is both complicated and straightforward: people may continue to test positive long past the point in which they are infectious.

To some employers, that’s a reason to stop relying quite so heavily on testing for answers. When the test given to everyone doesn’t answer whether or not they’re infectious, the choice is between erring on the side of extreme caution, or using symptoms and how much time has elapsed to take a calculated risk.

“We can’t test our way to safety,” said Dr. Allen Sills, the NFL’s chief medical officer. “Testing is important, but it is not the only important method or way to mitigate risk.”

Leading immunologists said that, as long as the league isn’t seeking guarantees, that policy is reasonable. But because of the lack of long-term, large-scale research on a disease that was identified mere months ago, they can’t tell you how confident they are in that assessment working in every single situation.

While the scientific community is still trying to fully understand who is still infectious, and to what degree, it’s increasingly backing this time-based strategy the leagues are deploying. “The bottom line is there’s always risk. You can’t be 100% sure,” said Ashish Jha, director of the Harvard Global Health Institute. “As a general policy and rule, it’s pretty reasonable.”

Understanding how in the world someone might test positive for the virus but also be completely safe to play a sport like football without further spreading the disease requires a basic understanding of the tests themselves.

The PCR test commonly used on both professional athletes and everyone else isn’t looking for viable forms of the virus—something that could actually pose a danger to others. It simply looks for whether there’s any viral genomic material.

That test also happens to be very sensitive. Someone could have the virus raging in their systems and be a threat to anyone they come into close contact with. They could also just have fragments or remnants of the virus that are no longer dangerous to anyone. Both people could yield the same result on the PCR test for Covid-19: positive.

“There definitely are a non-trivial number of people who continue to test positive for a longer period of time who we don’t think are infectious at all,” said Carl Bergstrom, a biology professor at the University of Washington.

What employers really need, and don’t have, is a test for infectiousness.

In research settings, Bergstrom says, there are ways to determine whether someone is infectious. But that’s not the case for either the general public or these billion-dollar sports leagues. “We don’t have the gold standard level of proof that we’d like,” he said.

The leagues that play on with positive players may unwittingly help with that process of discovery. “It’s within the boundaries of good practice,” said Lawrence Steinman, an immunologist and neurologist at Stanford University, who has written many publications using PCR.

“Whether there will be leakiness,” Steinman added, “those are all things we’re going to learn.”

Write to Andrew Beaton at and Louise Radnofsky at