Arsenal striker Pierre-Emerick Aubameyang contracted malaria while on international duty with Gabon last month and spent time in hospital this week, he said on Thursday.
Aubameyang played one match for Gabon as they booked their place in the Africa Cup of Nations finals and he has started one Arsenal game since returning to England.
"Unfortunately, I contracted malaria whilst being on national team duty in Gabon a few weeks ago," Aubameyang wrote on Instagram.
The 31-year-old striker was not in the Arsenal squad when they beat Sheffield United on Sunday. He also did not travel for the second leg of their Europa League quarterfinal at Slavia Prague on Thursday, which Arsenal won 4-0 to advance to set up a semifinal match against Villarreal and former Gunners manager Unai Emery.
"I've spent a few days in hospital this week, but I'm already feeling much better every day, thanks to the great doctors that detected and treated the virus so quickly," Aubameyang added.
"I wasn't really feeling myself the last couple of weeks but will be back stronger than ever soon."
Arsenal, who are ninth in the Premier League standings, host Fulham on Sunday.