During this past week, the NFL has seen players on multiple teams test positive for the coronavirus, and others placed into quarantine under new, more stringent protocols for those considered high-risk contacts. But in what is considered the league’s new normal, all Week 9 games remained on schedule, including the Green Bay Packers’ victory over the San Francisco 49ers on Thursday night, in which each team was missing one player who tested positive.

If all of this week’s games are played, that will make it four straight weeks with little to no disruption of the schedule on the heels of two weeks that included rampant rescheduling.

The NFL is about to pass the midway point of its 17-week regular season as it attempts to become the first major U.S. sport to play a full and uninterrupted season since the pandemic began. The schedule has been juggled. Teams have played in empty or partially filled stadiums. But the NFL trudges onward, hoping to reach the Super Bowl set for Feb. 7 in Tampa but mindful that tougher times could be ahead.

“This is an incredibly tough opponent,” Allen Sills, the NFL’s chief medical officer, said this week. “We’ve said all along: This is a very hard job. This is an easily transmitted virus, and we see that the levels are rising out in the community. And so that just puts us all at greater risk.”

The NFL and the NFL Players Association say that under their testing program, more than 550,000 tests were administered between Aug. 1 and Oct. 31 to players, coaches and selected team staffers, with 63 players and 99 coaches and staffers testing positive.

“I think that we can feel like that our clubs have done a really good job overall,” Sills said. “But by no means is the work done. It’s going to get harder.”

The league has fined players, coaches and teams to try to compel compliance with protocols. It stripped a sixth-round draft pick from the Las Vegas Raiders.

Protocols have been adjusted as the season has progressed. The league and NFLPA eliminated the one exception to their daily testing when they added game-day testing. In a memo this week, the NFL urged teams to ask all players to wear masks on the sideline during games, as is required of coaches and staffers. The league told teams that mask-wearing by players is required during any pregame or postgame interactions. The NFL also lengthened the bench area for each team during games to promote distancing measures.

But perhaps the most significant tweak to the sport’s extensive protocols came when the NFL decided recently to mandate five-day quarantine periods for those categorized as high-risk close contacts to an individual infected with the virus. The decisions about which contacts are classified as high risk are based on time, distance, whether a mask was present and how much ventilation might have been involved, according to Sills.

The new approach has amounted to a trade-off, creating more roster-management complications and competitive issues for teams in exchange for decreasing the likelihood of an outbreak.

The Jacksonville Jaguars placed 13 players on their covid-19 reserve list (used both for players who test positive and those exposed to the virus) on a single day. The Raiders practiced one week without their entire starting offensive line. The New York Giants sent home seven of their 11 offensive linemen one day but had six of them return the following day when they weren’t officially classified as high-risk contacts.

But the NFL has avoided another outbreak such as the one experienced in late September and early October by the Tennessee Titans; after 24 members of the organization tested positive, two Titans games were rescheduled, one of which became the NFL’s second Tuesday game in 74 years. So far, the NFL has not had to add a Week 18 to the regular season, which it has said it would do only if it cannot play all the games within the current framework.

And if any teams are displeased about having so many players placed in quarantine, the NFL’s advice is: Wear a mask and keep your distance, and you’re far less likely to be classified as a high-risk close contact.

“Our focus and efforts really continue to be on limiting those exposures, particularly for the high-risk close contacts,” said Dawn Aponte, the NFL’s chief football administrative officer. “As we’ve said before, those high-risk close contacts are really things that are within the clubs’ control and individuals’ control.”

On Thursday and Friday alone, at least 10 NFL teams saw a positive test result for a player, coach or team staffer. Some of those teams worked remotely. Others held in-person practices. Numerous teams operated this week under the intensive protocols for a team with a coronavirus case or exposed to the virus.

“Those measures certainly make it so that they have lower risk,” said Tara Kirk Sell, a senior scholar at the Johns Hopkins Center for Health Security. “But is it low enough to mean they’re going to make it through? I mean, we’ve already seen it’s really not. They’re going to have cases. How many teams in the NFL have cases right now?”

The NFL said all along that it expected to have coronavirus cases. But its recent ability and willingness to deal with positive test results while keeping games on schedule has not gone unnoticed.

“Just an observation,” former Packers executive Andrew Brandt wrote at midweek on Twitter. “In March there was one positive test in the NBA and it shut down all of sports for months. Now there are positive tests on both teams playing an NFL game [Thursday] night, and it’s game on.”

The decisions to postpone games have been based on concerns about transmission of the virus, according to Sills.

“I would say in those instances where we’ve postponed games,” Sills said, “it’s been where we have what we consider to be ongoing transmission for which we don’t have as much of an understanding. … I would just say that we’ve had a large number of situations where we’ve had one positive test, a small number of high-risk contacts and clubs have been able to safely continue operations through that time.”

The league realizes its toughest challenges are ahead as it frets about protocol fatigue by players, coaches and staffers and potential compliance issues with teams out of the playoff race. Deteriorating conditions nationally are a concern. One person familiar with the NFL’s planning said the “vast majority” of the sport’s coronavirus cases result from exposures outside teams’ facilities, adding: “If someone goes to his dentist [and is exposed], there’s no stopping that.”

With caseloads rising in many states and winter nearing, Sills said: “We continue to consider that every one of our 32 clubs are vulnerable to infection every single day that we’re in business, just like all of us are around the country right now. We have to all just continue to be extremely vigilant about the measures that we know that mitigate risk.”