An outbreak of norovirus has closed three wards at Royal Cornwall Hospital.
Staff have made the closures at the hospital to reduce the spread of infections.
The hospital is operating on its highest level of alert and is urging patients with norovirus symptoms to visit their GP or to stay at home.
Two community hospitals have also been closed.
Norovirus is highly contagious.
It tends to last between 12 and 72 hours and symptoms can include vomiting and diarrhoea.
Norovirus is sometimes referred to as the ‘winter vomiting bug’ and this summer outbreak is seen as unusual.
The advice for people suffering with norovirus symptoms is to drink plenty of fluids, rest and take pain relief when necessary.
Other tips are to keep your environment clean and don’t go back to work or send your children back to school too soon.
The most important piece of advice is avoid health care settings unless in exceptional circumstances and if you need advice to try the 111 service first.