An independent school has been struck by an outbreak of measles which is believed to have affected up to 20 children.
The Health Protection Agency has confirmed it is investigating the outbreak at the Sands School, a £8,310 per year private school near Ashburton in Devon. It has around 70 students aged between 11 and 16.
The HPA has sent parents letters telling them to make sure their children have received the MMR vaccine and urged people across Devon to check their children's inoculations.
"So far several children have been kept away from the school with measles-like symptoms and one student has been laboratory confirmed with measles. This confirmed case is now fully recovered and back at school," an HPA spokesman said.
"Information letters have been sent to all parents giving information about the symptoms of measles and advising that any children who have not had the full course of two MMR jabs should be immunised as soon as possible. GPs in the area have also been asked to offer immunisation to any children who have not had the full protection of two MMR jabs in the past."
Dr Geoffrey Thould, of the South West (South) Health Protection Unit, added: "Measles is a very infectious virus, and can spread rapidly in close knit communities such as schools if people have not been immunised.
"While most people who catch measles will recover completely within a couple of weeks, it's important to remember measles can be a very serious illness that can leave permanent disability, and occasionally even kill.
"Because we have recently seen this rise in cases, I'd appeal to any parents who have not yet had their children vaccinated to get them protected as soon as possible. I would like to reassure parents that MMR is a safe, effective vaccine.
"Children should receive two doses of MMR vaccine for maximum protection, and MMR doesn't only protect them, it also limits the chances of the virus spreading more widely, for example to children who are too young to have the vaccine, people with weakened immune systems or pregnant women."
The school, which bills itself as "the alternative face of education", works on democratic lines, with children encouraged but not forced to attend lessons.
HPA statistics show a huge rise in the number of measles cases in 2011 compared with 2010.
There were 334 cases of confirmed measles in England and Wales contracted between January 1 and April 30 this year, compared with 374 cases for the whole of 2010.
A spokeswoman for the Sands School said it had notified all parents of the outbreak and was following the HPA's advice. It was also talking to neighbouring schools to avoid any possible spread of the infection.
"Everything is as normal here," she said.
"We have one confirmed case and possibly several others. Most of our students have finished their exams, it hasn't really affected school life."