For months, the NFL rigorously tested symptomatic and asymptomatic players alike for the coronavirus. Now, the league says asymptomatic players aren’t spreading the virus.

During an interview on the NFL Network, NFL Chief Medical Officer Allen Sills says that “the overall pattern and concern about transmission, it is not being driven by people who have no idea that they are infected and they are infecting scores of others. This is being driven by people with symptoms and the exposures during that symptomatic period.”

Sills continued:

I think all of our concern about [asymptomatic spread] has been going down based on what we’ve been seeing throughout the past several months. We’ve got our hands full with symptomatic people. Can I tell you tonight that there has never been a case when someone without symptoms passed it on to someone else? No, of course I can’t say that. But what I can say to you is that I think it’s a very, very tiny fraction of the overall problem, if it exists at all.

Clearly if you want to look at the overall pattern and concern about transmission, it is not being driven by people who have no idea that they are infected and they are infecting scores of others. This is being driven by people with symptoms and the exposures during that symptomatic period.

The concern over the potential spread of the disease from asymptomatic players and coaches arose after the league changed its testing policy last week. In response to a surge of over 100 positive tests in a 72-hour time span, the league changed its testing regimen from regular weekly testing of symptomatic and asymptomatic players to rolling testing of teams and position groups as well as only symptomatic players.

TAMPA, FLORIDA – FEBRUARY 07: Signage about Covid-19 protocols is seen before Super Bowl LV between the Tampa Bay Buccaneers and the Kansas City Chiefs at Raymond James Stadium on February 07, 2021 in Tampa, Florida. (Photo by Patrick Smith/Getty Images)

This shift in philosophy caused some to voice concerns that untested asymptomatic players could unknowingly spread the disease in locker rooms across the league. However, according to Dr. Sills, that concern is unfounded.

“Asymptomatic transmission inside our facilities just didn’t fit with what we were seeing,” Sills told ESPN.

The NFL’s abrupt departure from its testing norms represents not only a break with its own past but also the conventional wisdom of public and private health authorities who for months have warned that asymptomatic individuals could be prime spreaders of the disease.

TAMPA, FL – JANUARY 30: National Football League fans convene in downtown Tampa ahead of Super Bowl LV during the COVID-19 pandemic on January 30, 2021 in Tampa, Florida. (Photo by Octavio Jones/Getty Images)

A widely circulated study published in January estimated that more than half of all Covid transmission cases.

“More than 94% of players and nearly 100% of coaches are vaccinated. A total of 46 players tested positive Thursday, according to ESPN’s Field Yates, bringing the total to 154 this week and more than 300 in the past two weeks,” ESPN reports.

It is unknown if other leagues plan on adopting the NFL’s new testing methods.