Jose Ramirez's WBC and WBO light-welterweight title defence against Ukrainian Viktor Postol has been postponed because of the coronavirus outbreak in China.
The bout was set to take place in Haikou on 1 February, with speculation the winner would take on Britain's Josh Taylor in a unification fight.
The virus has killed 18 people in China.
"We hope the situation is brought under control soon," promoter Bob Arum said.
"The health and safety of our fighters and everyone working on the event is the most important thing."
The fight will be contested at a date and venue to be determined, promotion company Top Rank said.
Both Mexican Ramirez, 27, and Taylor, 29, are on the Top Rank books.
Taylor holds the WBA Super and IBF light-welterweight titles.