Football can be the "perfect setup" to spread the coronavirus, so diligent testing and how the nation responds to a second wave of the virus in the fall will help determine what the 2020 NFL season could look like, Dr. Anthony Fauci told NBCSports.com.

"The virus will make the decision for us," said Fauci, the director of the National Institute of Allergy and Infectious Diseases and a key member of the White House task force on the virus.

The NFL has time on its side: The regular season is not scheduled to begin until Thursday, Sept. 10, when the Kansas City Chiefs will host the Houston Texans. A full day of games is scheduled for Sunday, Sept. 13. Fauci said right now "there's too much infection" for there to be a season, adding, "But I would hope that by the time you get to September, it's not gonna be the way it is right now."

Fauci explained to NBCSports.com that sweat is not a threat to spread the virus, but the danger of players shedding the virus would still be high during a football game.

"This is a respiratory virus, so it's going to be spread by shedding [the] virus. The problem with virus shedding is that if I have it in my nasopharynx, and it sheds and I wipe my hand against my nose -- now it's on my hand. You see, then I touch my chest or my thigh, then it's on my chest or my thigh for at least a few hours. Sweat as such won't transmit it. But if people are in such close contact as football players are on every single play, then that's the perfect setup for spreading. I would think that if there is an infected football player on the field -- a middle linebacker, a tackle, whoever it is it -- as soon as they hit the next guy, the chances are that they will be shedding virus all over that person.

"If you really want to be in a situation where you want to be absolutely certain, you'd test all the players before the game. And you say, 'Those who are infected: Sorry, you're sidelined. Those who are free: Get in there and play.'"

Players who tested positive for the virus should be quarantined for 14 days, Fauci told NBCSports.com.

Fauci said testing multiple times per week would be most effective because, "If I test today and I'm negative, you don't know if I got exposed tomorrow."

He gave an example of how he recently was exposed to an infection in the White House. He was tested immediately and was negative, but that doesn't mean he'd be negative the next day. Testing every day isn't "practical," but the NFL could diminish the possibility of spread "dramatically by testing everybody Saturday night, Sunday morning, and say, OK, only negative players play."

He said "it's feasible that negative testing players could play to an empty stadium" and if the virus level in the nation is low enough that the risk is for fans is low, he "could see could see filling a third of the stadium or half the stadium so people could be 6 feet apart."

Fauci said ultimately a football season "will be entirely dependent on the effectiveness with which we as a society respond to the inevitable outbreak that will occur" in the fall.

"So, practically speaking, the success or failure, the ability or not, to actually have a football season is going to depend on just on what I said ... but what I'm really saying is it's unpredictable depending upon how we respond in the fall," he told NBCSports.com.