All three of Bristol's main hospitals have been affected, as has the Royal United Hospital in Bath.

Three wards at Bristol Royal Infirmary (BRI) are shut and tests are under way to find which virus is responsible.

In Somerset, Musgrove Park Hospital in Taunton and Weston-super-Mare General are said to be only just operating to full efficiency after also being hit.

Warning to visitors

Staff and visitors entering the affected wards at the BRI are required to clean their hands with an alcohol rub first.

Chris Perry, who is in charge of infection control, said: "We are still sending specimens to the laboratory to get an idea of what's going on. It's usually something like Norovirus, which was formerly known as Norwalk virus."

"We are asking visitors and staff not to come to the hospital if they have got diarrhoea and vomiting."