Conor McGregor had to cancel his New Year's Eve plans after he and his family were struck down by an Australian flu.
The 29-year-old took to Instagram in a post - that has since been deleted - to tell his fans about the illness that left him bedridden and other family members hospitalised.
He wrote that the illness had left him "shaking in bed".
"Well that was a wild New Year's Eve. Half the family hit with the Australian flu virus and some even left in hospital with it," he wrote.
"I've never even been to Australia wtf.
"One of the most intense few days I've gone thru. Big New Year's Eve party cancelled at the last minute and I am left shaking in bed the past two days.
"I'll leave that with the rest of the bad behind me in 2017 and take with me the many great experiences I've had this year! None greater than the birth of my son Conor Jr. and the continued support of my family, my friends and my dedicated staff through thick and thin."
He capped off by wishing his fans - and the press - a happy new year.
"Thank you all and Happy new year to everyone!" he said.
"2018 I may go back to the back pages instead of the front pages again but I have a feeling these journalists now just want me in the obituary pages so we shall see. I will be ready for whatever comes.
"Be sharp and be fast this year because I am sharper and I am faster. God bless you all and Happy New Year!"