The Pac-12 Conference announced Tuesday that it has postponed the 2020 football season because of safety concerns stemming from the novel coronavirus pandemic. With the Big Ten announcing its decision to cancel the fall sports season earlier in the day, only three of college football’s elite Power Five conferences plan to play this fall.

The Pac-12 will not hold any athletic competitions until after Jan. 1. The decision affects all fall sports and some winter sports, such as men’s and women’s basketball, which typically begin their seasons in November. The conference said in a statement that it would consider holding games for the affected sports after Jan. 1.

College football players returned to their campuses in June for voluntary workouts, but as the fall season approached and the virus continued to spread throughout the United States, a path forward became uncertain.

“The health, safety and well-being of our student-athletes and all those connected to Pac-12 sports has been our number one priority since the start of this current crisis,” Pac-12 Commissioner Larry Scott said in a statement. “Our student-athletes, fans, staff and all those who love college sports would like to have seen the season played this calendar year as originally planned, and we know how disappointing this is.”

The Pac-12 had previously planned for its 12 teams to play conference-only schedules beginning Sept. 26. Fall practices would have started as early as Aug. 17.

Numerous athletes, coaches and politicians, including President Trump, have publicly pushed for schools to play football this fall, but some players and decision-makers have concerns about the long-term effects of the virus. Health experts are worried about how covid-19, the disease caused by the coronavirus, affects the heart. More than 30 Power Five football players have already decided to opt out of the 2020 season.

On a teleconference session with media members after the Pac-12′s announcement, conference officials cited recent indications that the coronavirus could cause cardiovascular issues for athletes as a major factor in their decision.

“There is emerging data about some health risks … that we don’t know enough about,” said Doug Aukerman, the senior associate athletic director for sports medicine at Oregon State who also serves as the head of the Pac-12′s Covid-19 Medical Advisory Committee.

“Once we started becoming more concerned about some of the side effects and some of the other health outcomes, that we don’t know what the short-term and long-term consequences are yet, we felt that we have to shift to a mind-set of not just trying to stop the spread, but we need to be able to identify anybody who has the coronavirus right away,” Aukerman said. “And that becomes incredibly difficult when you’re in a community where the spread is not controlled.”

“We wanted to really give [a fall season] the best shot, but in the end we looked at the recent cardiac evidence,” Michael H. Schill, president of the University of Oregon, said during the session. “We looked at spread, which was increasing in some of our areas, we looked at government directives, and we just said there’s too many questions, too much uncertainty. So we will continue to assess, and hopefully we will be playing in the spring.”

“We are science-based. We’re academics,” Schill added. “We are going to be looking at facts, and not just opinions.”

The Pac-12 is the fourth FBS conference to cancel its fall season. The Mid-American Conference postponed its football season Saturday, becoming the first FBS league to do so. The Mountain West followed suit Monday, and Old Dominion, a member of Conference USA, also announced it would not play this fall, even though its league plans to move forward toward the season.

Two college football independents, the University of Connecticut and the University of Massachusetts, have also announced they will not play this fall. With the Pac-12′s announcement, 53 of the 130 FBS teams have either said they will not play this fall or are in conferences that have made that decision.

The loss of the revenue generated by football will devastate athletic departments, and it’s unclear how much could be made up if teams are able to play this spring. The millions of dollars each school receives through football broadcast rights fuel the operating budgets of athletic departments that support many nonrevenue programs.

Stanford announced in July that it would discontinue 11 programs following the 2020-21 academic year. In a letter announcing this decision, the university said that because of the coronavirus, the athletic department’s projected “best-case scenario” was a $25 million deficit during the 2021 fiscal year.

Scott, the commissioner of the Pac-12, said in Tuesday’s media session that “TV contracts did not even come up today” as the conference made its final decision regarding fall sports. Schill said there was no “drama” or major disagreements among the Pac-12′s CEO group, composed of one president or chancellor from each of the conference’s 12 universities, during the meeting that day.

Pac-12 football players released a unified statement Aug. 2, threatening to boycott practices and the season if demands related to safety protocols, racial justice and player compensation were not met by the conference. Last week, the players said in a letter to Scott that, after speaking with him, they were “left disappointed that you are not taking this matter seriously.”

With uncertainty about the season growing, the Pac-12 players collaborated with their peers from the other Power Five conferences. On Sunday night, players shared a social media message that featured #WeWantToPlay and the Pac-12′s #WeAreUnited hashtags. A graphic accompanying the players’ tweets outlined that they wanted to play this season, but they also wanted mandatory health and safety protocols and other assurances related to their scholarships and eligibility.

Despite that public push, the Pac-12 presidents decided that the health risks of a fall season were too great to move forward.