Comedian David Walliams is reportedly undergoing tests for Weil's disease after swimming the River Thames for Sport Relief earlier this month.
Walliams was admitted to hospital to treat a back injury following the challenge, and now The Sun report he is being tested for potentially fatal Weil's disease, a waterborne condition, after displaying symptoms - including fevers and muscle pain.
A source tells the publication, "The first signs were during the swim - the sudden fever, the diarrhoea and the rash. What was especially significant was the sudden stop of the illness only to return a few days later.
"The extreme and continued muscle and joint pain and the fact he is still extremely fatigued and feverish show all the classic signs of Weil's. He is undergoing tests but at least he's in good hands."
Walliams raised £1million for charity from his eight-day swim, which finished in London earlier this month.