Daybreak's Health Editor Dr Hilary Jones has told viewers that Norovirus is "very bad news".
He said: "Although it's not hugely a life-threatening it is the most common form of gastroenteritis in adults in the UK."
More top news
Armed police were out in force as runners competed in the largest public event in the city since Monday's terror attack.
Taliesin Myrddin Namkai Meche, 23, was stabbed along with Rick Best, 53, when they tried to stop a racist attack on two Muslim girls.
The shadow home secretary, 63, said she worked in the Home Office for nearly three years when she was a trainee.