The NFL’s chief medical officer said Friday that the novel coronavirus outbreak on the Tennessee Titans is “an evolving situation” being monitored and reevaluated daily, adding that the league will not reopen the team’s facility until it is “convinced that we’ve reached the end of the transmission event that occurred earlier this week.”

Allen Sills said in a phone interview he is “still cautiously optimistic” about the NFL’s prospects to complete its season as it operates amid the pandemic, even while dealing with this first outbreak that caused the postponement of Sunday’s scheduled game in Nashville between the Titans and Pittsburgh Steelers.

Sills’s comments came as two additional Titans players tested positive in results returned Friday, creating concerns that the outbreak could be an issue beyond this week and threaten more than the one game. Three more members of the organization, including one player and two non-players, tested positive in results returned Saturday.

“I can’t really give you a timeline or a number at this time,” Sills said Friday. “I’ll just say that we continue to monitor and it’s obviously an evolving situation that we’ll continue to watch closely on a day-by-day basis. We don’t want to reopen the Titans’ facility until we’re convinced that we’ve reached the end of the transmission event that occurred earlier this week and that we have put in place all the measures to keep everyone safe there.”

The Titans next are scheduled to play Oct. 11 against the Buffalo Bills in Nashville.

The NFL announced Friday that it had rescheduled the Titans-Steelers game for Oct. 25 in Week 7. That was the Titans’ originally scheduled bye week. The Steelers’ Week 7 game at Baltimore was moved to Nov. 1 in Week 8, the original bye week for both the Steelers and Ravens. Those are the first coronavirus-related changes to the NFL’s 2020 regular season schedule.

“I remain still cautiously optimistic as we move forward,” Sills said. “We’ve said consistently throughout that this is going to be very difficult. And we’ve also said that we expect to have positive cases. So I think that our protocols and our procedures are designed with this scenario in mind. We certainly hope and pray that it never happens, but we’re prepared when it does. And I think that we will learn and get better from this set of circumstances. We’ll learn additional measures that we can take to keep everyone safe. And I think that this will also serve as a reminder to everyone how vigilant we have to be and how difficult this is.”

The two positive test results Friday for the Titans were confirmed by two people familiar with the situation. One of those people, speaking on the condition of anonymity because of the sensitivity of the topic, said the growing number of positive tests for the Titans is raising concern as a potential issue beyond this week.

Saturday’s results, confirmed by a person with knowledge of the matter, mean that 16 members of the Titans’ organization have tested positive this week, including eight players and eight team staffers. Coach Mike Vrabel said Thursday he was hopeful that his team would be permitted back into its facility early next week under enhanced health and safety protocols.

“The events of this week are exactly why we planned and put the protocols in place that we have,” Sills said Friday, stressing that the NFL has focused on risk mitigation while acknowledging that entirely avoiding positive cases is virtually impossible. “We had a plan and a preparation there to walk through when this unfolded.”

According to Sills, NFL Commissioner Roger Goodell stressed that the Titans’ situation is to be handled with health and safety as the priority, without regard to scheduling or competitive considerations. The league continues to work to try to trace the origins of the Titans’ outbreak, Sills said.

Sills said there are “some symptomatic individuals” in the Titans organization, adding: “Fortunately to this point they have been relatively mild symptoms and no one has required more intensive medical care.”

The facilities of the Titans and Minnesota Vikings, who played Tennessee on Sunday in Minneapolis, were closed Tuesday after the first set of positive test results for the Titans. The Titans have had at least one new positive test result each day this week.

The Vikings had no positive tests in the results returned Saturday, according to a person familiar with the situation. They have had no positive tests this week and reopened their facility Thursday under enhanced protocols outlined by the league to teams in a memo. The NFL plans for the Vikings’ game against the Texans in Houston to be played as scheduled Sunday.

Sills said it’s possible some of those enhanced protocols, which include increased testing and mandatory mask-wearing by players and team staffers on the practice field, eventually could be incorporated into the NFL’s standard protocols for all teams.

“It’s going to depend on the continued evolution of this situation and also what we learn from our epidemiologic investigation,” he said. “Our goal is simple: We want to keep everyone as safe as possible in all environments at all times. So we’ve said that we learn from each of these events. … Since this is our first outbreak, we’ll certainly learn from this."

The NFL told teams in a memo Friday that it had reached an agreement with the NFL Players Association to extend daily coronavirus testing of players, coaches and some team staffers, except on game days, “until further notice.” The new agreement includes provisions for daily testing of players and coaches during teams’ bye weeks, according to the memo. Players and coaches cannot leave a team’s home city during the bye week and must submit to daily testing.