UFC 249 is going ahead tonight with safety rules in place attempting to mitigate the risk of fighters catching the Covid-19 coronavirus.
Fighters have been tested throughout the week and on the eve of fight night, one of those tests threw up a positive result.
Brazilian middleweight Ronaldo 'Jacare' Souza tested positive along with two of his cornermen.
"From their arrival earlier in the week until their departure today, Souza and his cornermen followed UFC health and safety protocols, including practicing social distancing, wearing personnel protective equipment, and self-isolating whenever possible," a UFC statement read.
"There have been no other positive Covid-19 tests reported from the remaining athletes participating in UFC 249. The response to this development is indicative of the effectiveness of the health and safety measures UFC has put in place for this event."
At the age of 40, Souza is a veteran of MMA with a professional record of 26-8.
After rising through various promotions including Strikeforce, the Brazilian jiu-jitsu specialist made his UFC debut in 2013.
He has taken down some big names in his UFC career such as countryman Vitor Belfort and former UFC middleweight champion Chris Weidman. He also defeated Robbie Lawler in Strikforce back in 2011.
Souza - whose nickname 'Jacare' means 'alligator' - has three children with his wife Larissa Carvalho.
Souza holds eight World Jiu-Jitsu Championship gold medals.
His scheduled opponent Hall, who will now not compete, tweeted Souza: "Brother I know it sucks. I'm sorry you have to go through this I am beyond devastated for the missed opportunity. I wish you nothing but recovery for you and your family."
Conor McGregor also wished him luck, saying: "Wishing all my fighting colleagues good health as they put on tonight’s show for us! #UFC249 on ESPN+ Good luck and God speed men and women.
"From the competitors to the cleaners. Thank you all Also Prayers up for Jacare Souza and team in making a full recovery. #UFC249#ESPN"
