A Norovirus outbreak has been reported at the Royal Cornwall Hospital in Truro, as well as in a care home and a nursery in the county.
There are bay closures in three wards at the hospital Royal Cornwall Hospital and anyone with symptoms of vomiting and/or diarrhoea are asked to stay away from work or school until they have been symptom free for 48 hours.
A spokesman for Kernow Clinical Commissioning Group said: "Outbreaks of norovirus can cause major disruption to both community and hospital settings. To help minimise this, patients with symptoms should not visit their GP unless the symptoms last longer than 48 hours. Those with a planned hospital admission should inform the hospital in advance and those with symptoms should not visit anyone in a hospital or care home.
It is estimated that Norovirus affects between 600,000 and a million people in the UK each year. Outbreaks can affect more than 50 per cent of susceptible people and usually tend to affect people who are in environments such as hospitals, nursing homes and schools.
The most effective way to respond to an outbreak is to disinfect contaminated areas, to institute good hygiene measures including hand-washing and food handling.