Eating out, poor hand hygiene and erratic weather may be among causes, say medics
Ronaldo, 34, has won the renowned France Football magazine trophy for the world's best player five times - as many as Messi - but is eager for more as he moves into the twilight of his career.
"Messi's in the history of football," Ronaldo told broadcaster Piers Morgan in an interview with Britain's ITV on Tuesday. "But I think I have to have six or seven or eight to be above him," he said, referring to the Ballon d'Or awards.
"I'd love it, I think I deserve it."
The Portugal captain said he was no friend of the Argentine but credited his rival for helping push him further in his own career.
"My relationship with him is, we are not friends, but we have shared this stage for 15 years," Ronaldo said. "I know that he has pushed me to be a better player and I have pushed him to be a better player as well."
Ronaldo, who also played for Manchester United and Real Madrid, has five UEFA Champions League winners' medals and led Portugal to victory at the 2016 UEFA European Championship and 2019 UEFA Nations League tournaments.
"I don't follow the records, the records follow me. I'm addicted to the success, and I don't think it's something bad, I think it's good," Ronaldo said.
"It motivates me. If you're not motivated, it's better to stop."
Eating out, poor hand hygiene and erratic weather may be among causes, say medics
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