The Health Protection Agency (HPA) is urging parents to have their children vaccinated against measles, after two confirmed cases of the illness.
Both were reported in Manchester in the past three weeks and are the first in the city since 2006.
The HPA says it is vital that children are given two doses of the MMR vaccine to protect them against the disease.
The agency says that a third of five-year-olds are vulnerable as they have not been properly immunised.
Dr Rosemary McCann, the Health Protection Agency North West's regional immunisation lead, said: "These cases prove that it is vitally important for children to have both doses of MMR, which will give life-long protection against measles, mumps and rubella.
"These are potentially serious illnesses and more than one-in-three five-year-olds in Manchester are vulnerable to them because they have not had the two doses of MMR that is needed to protect them.
"We are advising parents that if their child has missed one or both doses of MMR, they should contact their GP, practice nurse, health visitor or school nurse to arrange vaccination."
'Serious complications'
Measles is an infectious viral illness that is spread by droplets in the air when infected people cough or sneeze. The most common symptoms are fever, cough, sore eyes and a rash.
Most patients make a full recovery, but some will experience serious complications that can include pneumonia and meningitis and can, on rare occasions, prove fatal.
Dr Sally Bradley, Director Public Health with Manchester PCT, said: "Measles can be a serious illness with the potential for nasty complications. That is why it is so important for parents to protect their children with two doses of MMR vaccine.
"The vaccine is usually given to children at around 13 months old, with a second dose before they start school.
"Although we are only aware of a small number of cases at present, with so many unvaccinated children in Manchester, there is a high risk of further spread if we don't take action."
^ Back to top | BBC Sport Home | BBC Homepage | Contact us | Help | ©
~RS~q~RS~~RS~z~RS~38~RS~)