A Bristol health trust has closed five hospital wards after an outbreak of the stomach bug Norovirus.
Four of the wards were at Southmead Hospital, the other at Frenchay, a spokesman for North Bristol NHS Trust said on Monday.
The virus is spread by contact with people suffering diarrhoea, vomiting or contamination in the environment.
Some patients do not realise they are already incubating the virus when they go into a hospital.
"Airborne spread occurs during episodes of vomiting, to those in close proximity at the time," the spokesman added.
Symptoms appear 12 to 48 hours after exposure to the virus and can last for up to three days.
Carol De Halle, deputy director of nursing, added: "We strongly urge visitors with symptoms to please avoid visiting the hospital until symptoms have completely settled for two days."