The number of people in the South West who have gone to their doctor complaining of stomach bugs has trebled in the past few months.
Norovirus - which is also known as the winter vomiting bug - is easily spread and outbreaks are difficult to control.
Symptoms include sudden onset of nausea followed by projectile vomiting and diarrhoea. Some people also get a high temperature, headaches and aching limbs.
People in hospital are particularly at risk. Many hospitals including the Devon and Exeter Hospital have restricting visiting hours with a number of wards also closed.