The now-retired 35-year-old made the announcement after posting a picture of himself on Twitter receiving treatment for the infectious disease.

"Good morning to you. I have started the year with dengue," wrote Ronaldo, who had been celebrating the new year in Trancoso, Bahia.

"Thank you for caring. I'm in recovery."

"I was released (on) Tuesday night. Now for treatment and rest and to get well soon!!!"

Dengue is transmitted by several species of mosquito and can, in a small proportion of cases, develop into a life-threatening condition.

Ronaldo, the all-time leading scorer in World Cup history with 15 goals, called time on his illustrious playing career last year after struggling for a long time with weight problems and the effects of a succession of injuries.