The number of cases of measles has reached its highest level for 18 years, health experts have said.
The majority of cases of the highly infectious disease have been recorded in Surrey, Sussex, and in Merseyside, as well as several smaller outbreaks.
There were 2,016 confirmed cases in England and Wales in 2012 - the highest since 1994, said the Health Protection Agency.
Symptoms include fever, cold symptoms, red eyes, sensitivity to light and greyish white spots in the mouth and throat. After a few days a red-brown spotty rash will appear.
People are protected against measles, mumps and rubella with the combine MMR vaccine - which is normally given as part of children's routine vaccinations.
The HPA said older children who were not vaccinated at the routine age, who may now be teenagers, are at particular risk of becoming exposed.