Mikaela Mayer tests positive for COVID-19, is taken off Top Rank card

"It came as a complete surprise. I am currently asymptomatic and am quarantining at an off-site location per recommended guidelines," Mayer, the NABF women's super featherweight champion, wrote. "The rest of my team tested negative and they are all in good health."

Mayer was to face Joseph on Tuesday as part of the Shakur Stevenson-Felix Caraballo card from the MGM Grand. The event — which will be held without spectators — will be the first boxing card in Las Vegas since the city's entertainment industry was shut down in March because of the global outbreak of the coronavirus. Casinos reopened just last week.

"I was really looking forward to bringing back boxing for all of you and I’m disappointed for myself, my team, my supporters and for my opponent, Helen Joseph, who worked just as hard to be here this week and put on a show for everyone," Mayer wrote.

Mayer, 29, is 12-0 with five KOs. She has defended her title three times, including a victory over Alejandra Soledad Zamora last October.