The Vikings remain scheduled to host the Falcons on Sunday at U.S. Bank Stadium after Atlanta closed its facilities Thursday because of a new positive test for COVID-19.

The Falcons are expected to reopen facilities Friday after an assistant coach tested positive, according to the Atlanta Journal-Constitution.

While the Vikings held practice Thursday at TCO Performance Center in Eagan, the NFL's chief medical officer, Dr. Allen Sills, said the decisions about closing team facilities and postponing games are based on how the league's medical experts gauge the risk of further transmission on a "case-by-case basis."

The Falcons, as of Thursday, have two positive tests this week — the unidentified coach and defensive tackle Marlon Davidson. But that doesn't rise to the level of the NFL keeping Atlanta's facilities closed beyond Thursday.

The NFL already has made calls both ways. The Patriots-Broncos game was postponed last week after New England shut its facility down for a second time Sunday morning, and the game already had been pushed to Monday night.

Meanwhile, the Titans, who have had more than 20 players and staff members test positive since winning in Minnesota on Sept. 27, played Tuesday night against Buffalo despite closing their facility the previous Sunday after another coach tested positive.

"That reflects the fact every one of these cases is different," Sills said Thursday on a conference call. "We have to judge the merits of what's going on based on the totality of the information we have — test results, the historical data, symptom reporting, our contact tracing interviews, video review inside the club. But what we're really trying to determine is, what do we think is the risk of ongoing transmission?"

Sills reiterated there has been "no evidence of on-field transmission from football-related activities," with the Vikings being the first major case study after having no positive cases from playing the Titans.

The Falcons and their most recent opponent, the Carolina Panthers, were placed in the league's "intensive protocols," which the Vikings experienced after playing Tennessee. Changes include all team meetings being conducted virtually, face shields and gloves being worn in practices, limited capacity in the weight room and limited time in the locker room.

"[The Falcons] have done a very good job there," Sills said. "The situation [Thursday] shouldn't change that fact. We've said all along we expect to have cases that occur, and in fact it's getting more challenging over these next few weeks because the disease is spiking throughout the country. So that means our players, coaches and staff are going to be more exposed when they leave the facility."

One major change in league protocols was made this week: Players, coaches and staffers with symptoms such as "sore throats, stuffy noses, coughs, [etc.]," per Sills, will now be sent home from practices or before games regardless of whether they tested positive for COVID-19. Browns receiver Odell Beckham Jr. was sent home Thursday with an illness despite not testing positive.

The return process, without an alternative diagnosis such as strep throat, requires two negative PCR tests taken at least 24 hours apart, meaning a player could theoretically develop symptoms Friday, Saturday or Sunday morning and miss a game without testing positive. Those decisions will be made by team medical staff and the NFL's infectious disease experts, Sills said.

"We certainly want to encourage people to report their symptoms," he added.

The Vikings are growing accustomed to adapting to changing protocols and schedules.

They've had an outbreak "dry run," as General Manager Rick Spielman described last month, when a New Jersey lab contamination in August led to 12 false positive tests, including eight players, and the Vikings enacted an emergency response plan with contact tracing and isolation.

After playing the Titans last month, the Vikings closed TCO Performance Center for two days and missed a practice while waiting to see if there was on-field transmission of the virus. The Vikings had no positive cases while returning to intensive protocols, which include two daily COVID tests.

Offensive coordinator Gary Kubiak said he's bracing for any outcome but first thought about friends in the Falcons organization.

"We all have friends, coaches on other teams, and when you hear something, the first thing you think about is, 'Everybody OK?' " Kubiak said. "It's just kind of part of the day nowadays, and you just pray that everybody stays healthy and we can keep plugging along."

Receiver Adam Thielen is tied for the NFL lead with six receiving touchdowns and just wants to add to that against the Falcons defense in a game currently scheduled for Sunday.

"We're trying to not even think about it," he said. "Not try to worry about those things, because that's just so far out of our control. So for us, we're just trying to pretend like nothing's going on and obviously listen to the protocols and follow them and try to do the best we can."