The BNP Paribas Open in Southern California, one of the world’s leading tennis tournaments, will not be held this month because of the spreading coronavirus, making it one of the highest-profile sporting events canceled in the outbreak.

Organizers of the event, in the Riverside County community of Indian Wells, made the decision on the eve of its start Monday after county officials declared a public health emergency when a case was confirmed in the area.

The tournament had previously announced Thursday that it would take various precautions in light of the virus, including having ball kids wear gloves and telling players not to handle pens or other items to autograph.

The decision came quickly and as a surprise to players, many of whom already were in Indian Wells preparing for the event. Many found out through social media Sunday evening when the tournament announced the decision. The tournament has never been canceled before.

Qualifying matches were due to begin Monday, with main draw matches beginning Wednesday.

Steve Simon, chief executive of the WTA Tour, said that officials had considered playing the tournament without spectators but rejected that option.

“We were supportive of the concept,” Simon said. “But ultimately the tournament didn’t feel it was in their best interest.”

The two-week tournament, which is a Masters 1000 tournament on the ATP Tour and one of four Premier Mandatory events for the WTA, would have concluded March 22. A smaller warmup tournament, the Oracle Challenger Series Indian Wells, concluded Sunday at the Indian Wells Tennis Garden, the same stadium where the BNP Paribas Open is held.

The tournament, which has colloquially earned “Fifth Slam” recognition for its large attendance and lucrative prize money, is the largest sporting event in the United States to be canceled over the growing concerns about the spread of the epidemic. Another large international event, the South by Southwest Festival in Austin, was canceled Friday.

Organizers of Indian Wells, as the tournament is better known, said they were unwilling to take a chance on going forward. More than 450,000 fans attended the tournament in 2018 and in 2019.

“There is too great a risk, at this time, to the public health of the Riverside County area in holding a large gathering of this size,” said Dr. David Agus, a professor of medicine and biomedical engineering at the University of Southern California, in a statement released by tournament organizers. “It is not in the public interest of fans, players and neighboring areas for this tournament to proceed. We all have to join together to protect the community from the coronavirus outbreak.”

California has reported 114 cases of the virus, including someone being treated at a hospital in Rancho Mirage in Riverside County. Gov. Gavin Newsom has declared a state of emergency.

There have been at least 539 cases counted in the U.S. across 34 states and the District of Columbia, with 22 deaths. Worldwide, there have been 109,400 cases and 3,800 deaths.

Tommy Haas, the Indian Wells tournament director, left open the possibility of playing his tournament at a later date in the crowded tennis calendar.

“We are very disappointed that the tournament will not take place, but the health and safety of the local community, fans, players, volunteers, sponsors, employees, vendors, and everyone involved with the event is of paramount importance,” Haas said. “We are prepared to hold the tournament on another date and will explore options.”

But finding another two-week window on the overstuffed professional tennis calendar in 2020 will be a challenge. It is unclear, however, whether other tennis events will still be staged.

The Miami Open, scheduled to begin March 23 and similar in prestige to the BNP Paribas Open, has not yet been canceled. The Ultra Music Festival, another major international cultural event scheduled for March in the Miami area, has been called off for 2020.

“The intent is still for Miami to operate,” Simon said. “It’s obviously two weeks away, but right now our approach is we are planning to operate all of our upcoming events and put every precaution in place. But we will obviously continue to work with the event very closely and will have to monitor all the situations there.”

The BNP Paribas Open is offering ticketholders refunds or credits toward tickets for the 2021 edition of the tournament.

The tennis tours shift to Europe in April for the clay season, which includes the Italian Open in Rome in May, a prestigious tournament in one of the countries most affected by the virus.

No subsequent tournaments at tour level have yet announced cancellations. Several smaller minor tournaments in China had been canceled previously, and a tournament in Bergamo, Italy, canceled its final.

Founded in 1974 and played under various names and in various locations, the BNP Paribas Open has become one of the pillars of the professional tennis tour since its move to Indian Wells in 1987. Larry Ellison, the tech tycoon and co-founder of Oracle, bought the event and the tournament complex, the Indian Wells Tennis Garden, in 2009. Since the purchase, new stadium courts and amenities have been added, and the tournament is regularly voted by the players as the best event in its category.

Although this is the first time the event has been canceled, in 1980 the tournament was not completed because of rain, and the men’s singles final was not contested.

Simon said the cancellation this year would be costly. “There will be losses for everybody,” he said. “But at this point this isn’t about the money per se. It’s about what is right, and I think it’s a challenging time right now.”