The 20-year-old actor, who plays Ron Weasley in the Harry Potter series, has suffered a 'mild bout' of the condition, his representative has confirmed.

He was forced to take a break in filming but is no longer contagious and has now returned to the set of Harry Potter and the Deathly Hallows - JK Rowling's final book.

And he is well enough to attend the world premiere of Harry Potter and the Half-Blood Prince in London on Tuesday.

His publicist said:"Other scenes were shot in his absence which did not require his involvement and thus filming was not disrupted.

"He has now recovered and is looking forward to joining his fellow cast members," his publicist said.

Grint has starred in all the Harry Potter films as well as British comedy film Thunderpants and the comedy drama Driving Lessons with Julie Walters.

Grint has also starred in all the Harry Potter films as well as British comedy film Thunderpants and the comedy drama Driving Lessons with Julie Walters.

Harry Potter and the Half Blood Prince is released in the UK on July 15.