There really can be no debate: The NFL has aced its initial efforts to practice and play amid the coronavirus pandemic. Since training camp practices began in mid-August, only seven players have produced positive test results. There have been no team outbreaks, and the only scare was caused by a contaminated private lab in New Jersey.

The success prompts two natural questions. First, are there any remaining obstacles to playing a full 2020 season, as league officials have said for months they plan to do? And second, can the protocols be loosened in any way while maintaining the current results?

The answer to the latter seems obvious. There is a strong internal push to get fans in more stadiums, wherever local and state regulations allow it. Ticket revenue is one motivation, of course, but fans would also enliven the otherwise awkward and sterile game atmosphere in empty stadiums. Commissioner Roger Goodell did not hide this ambition during a media call earlier this month.

"I believe," Goodell said, "that we will be having a lot of teams that start with no fans at the beginning of the season, and [then] evolve to fans."

Three teams hosted fans last weekend, in reduced capacities -- Kansas City, Jacksonville and Denver -- and four more will do so in Week 2. Goodell pledged to take a "cautious approach" and to cooperate with public health officials on all safety measures. To be sure, with the first 20 feet of seats in every stadium tarped off, players and coaches assuredly will maintain a safe distance from fans.

Regardless, some epidemiologists and infectious disease specialists said there is no way to eliminate the risk of bringing together thousands of people in a football stadium, ensuring there is a chance -- however slight -- that an NFL game could trigger community outbreak. Thursday, the Kansas City Chiefs announced that one guest at their Sept. 10 opener has since tested positive for COVID-19.

"Sports leagues like to talk about this in a binary way," said Zachary Binney, an epidemiologist at Oxford College of Emory University. "It's safe, or it's not safe. The truth is that everything should be viewed over the risk continuum. More people equals more risk. And it still hasn't been explained what is the benefit supposed to be. There's money for the teams. There's maybe a little bit of mental benefit for the people who get to go to the games. But I don't think that outweighs even a minor threat to the rest of the community.

"I'm not telling people they can't have football. I'm not telling them they can't watch it at home. I'm saying, please just don't go to the stadium. I don't think, with all the sacrifices that so many other people are making, that's an unreasonable request."

Let's take a closer look at both of our initial questions, utilizing the expertise of an epidemiologist, an infectious disease expert and an ethicist.

Fans in the stadium

In June, researchers at West Virginia University found a link between seasonal flu deaths and the presence of professional sports in United States cities -- and their oft-packed stadiums -- from 1962 to 2016. Because the flu spreads in similar ways to COVID-19, one of the authors of the paper said: "Opening pro sports games to fans is probably a terrible idea, in terms of public health."

Three months later, more is known about limiting COVID-19 transmission. NFL teams are cutting capacity by 80% or more. The Chiefs, for instance, announced attendance of 15,895 at Arrowhead Stadium for their opener, about 20% of capacity. Others are planning for similar restrictions. They are also implementing measures that include mandatory face coverings, symptom checks, dedicated entrances and separated "pods" in the stands.

Those policies might reduce the chance of spread, but they won't eliminate it. Contact tracing in Kansas City forced 10 people into quarantine who came into close contact with the individual who tested positive. It could take up to three weeks to know whether the disease spread among them or to anyone else associated with the game. And while teams can ensure that fans enter their assigned gate and are wearing masks at that point, they will have less control over enforcement of masking and physical distancing throughout a three-hour game.

"It has been documented in scientific literature that certain activities such as singing or yelling could lead to aerosolization of the virus," said Jill Weatherhead, an assistant professor of infectious diseases and tropical medicine at Baylor College of Medicine. "[That allows] the virus to stay suspended in the air and travel further, and that could facilitate super-spreader events. These activities, even at reduced stadium volume, could lead to outbreaks. The invitation of fans into football games that already involve large groups of players who are in close contact for hours is extremely risky. There is otherwise no data to support a certain number of fans that would be safe, and this should be heavily considered before allowing fans into a stadium during an uncontrolled pandemic."

The NFL has a bigger obligation than simply to comply with local regulations, said Don Heider, executive director of the Markkula Center for Applied Ethics at Santa Clara University.

"When you make a decision like this, it's not just about the players and the coaches and the teams and the fans," Heider said. "It's every person those people come into contact with. That's where it gets much more difficult. As ethicists, we would ask, 'What is the good here? If I'm trying to maximize good and minimize harm, what's the benefit of opening the stadiums up? And is that benefit worth a human life? More than one human life? Or a resurgence in the virus in the community?'"

The Chiefs and Jacksonville Jaguars, who hosted 14,100 fans in their Week 1 opener, both play in outdoor stadiums. In Week 2, two teams with hybrid facilities -- the Dallas Cowboys' AT&T Stadium and the Indianapolis Colts' Lucas Oil Stadium -- will enter the fray. Both stadiums have retractable roofs and sides. The Cowboys haven't confirmed how many fans they'll admit, but the Colts have capped their attendance at 2,500. Binney called indoor stadiums "far more dangerous for transmission of COVID-19," even if the roof and/or sides are open.

Ultimately, Heider said, teams have a "social responsibility" to their community even if it conflicts with what some fans might want.

"It's a tough decision," Heider said. "You hope each NFL team is really sitting down and having a serious discussion and analysis of what the ethical implications are, and what the long-term implications are, and if it's worth it to have X number of fans in the stands."

Complacency and community load

Binney was pessimistic about the NFL's pandemic approach when training camp began. The league had decided against the kind of "bubble" environment employed to great success by the NBA, WNBA, NHL and professional soccer. The NFL's protocols were closer to those of Major League Baseball, which suffered through a series of team outbreaks early in its return.

NFL players, coaches and staff would be subject to extensive masking and social distancing requirements while at the team facility. But as with those in baseball, they would be exposed to communities that in some cases were hosting raging virus spikes. Four summer hot spots -- Florida, California, Texas and Arizona -- are home to nine of the NFL's 32 teams.

This week, Binney admitted he is "stunned" at how well the league has fared.

"And I'm happy to be stunned," he said. "It has exceeded all of my expectations and, I think, many people's expectations. What we have seen is that these protocols can work for a period of several weeks when people are very vigilant. I have no reason to believe that the protocols are going to start to fail, but it's important to make the point that they're constantly in a very fragile situation, and constant vigilance is required."

Indeed, complacency might represent the NFL's biggest obstacle to continuing its season unabated. To this point, it's clear that NFL personnel are largely staying away from the kind of risky behavior that can increase the chances of infection. Daily testing and digital contact tracing, both cornerstones of the league's protocol, can help minimize the spread of a single infection, but those measures can get overwhelmed if a large number of people are infected simultaneously.

"An outbreak really can happen at any time," Binney said. "We've seen it in college football over and over and over again. If you don't follow the protocols and you're not careful, you can do something that would cause the virus to spread through the entire team. That can happen.

"But also, when a case does happen, it doesn't necessarily mean that somebody did something risky. Cases can arise even if you're doing your level best. Imagine a coach's kid is in day care. Another kid gets infected, or a teacher there is infected, and infects the kid. The coach comes home, hugs his kid and gets COVID-19. He didn't disobey any protocols. He did the best he could and still got infected."

The chances of such a scenario would increase if community cases rise, as many public health experts are predicting this fall as the flu season arrives and cooler weather forces more people indoors.

"The United States continues to have uncontrolled community transmission in many areas around the country," Weatherhead said. "Further uncontrolled community spread, and development of new hotspots, could jeopardize the success of football this fall and winter season, as well as jeopardize the health of players, coaches and community members. The higher the rates of community viral transmission, the greater the risk playing football will have for the athletes, staff and the community."

During the four testing periods that began Aug. 12, the NFL has had zero, four, one and two players produce confirmed positive results, respectively. There has never been more than 10 personnel from other areas of the team to produce confirmed positive results in a single period. In reality, the NFL has some wiggle room before an increase would jeopardize the current game schedule.

"The hope," Binney said, "is that daily testing and continued vigilance will still prevent outbreaks. So even if there is a seasonal worsening, maybe they go from one or two cases per week to maybe five or six cases but they're all isolated on different teams. So that would be an increase in cases, but not enough to derail the season. That would be the hope."