A growing number of children and teenagers have been hospitalised following an upsurge in cases of measles, doctors said yesterday.
Cases of the infectious illness have so far more than doubled nationally compared with the same period in 2011, affecting 51 children in the worst cluster in west Cork.
Official figures for the week ending May 19 show 64 measles cases were reported nationally, up from 31 during the same period in 2011. More young people have been affected since.
Two teenagers, who have the disease in west Cork, have been hospitalised, "showing just how infectious measles is", said Dr Kevin Kelleher, head of health protection in the HSE.
The fear is that, as the school holidays get under way, the disease will spread further among young people who have not been vaccinated.
"People will be travelling over the summer months, increasing the risk of coming into contact with measles," he said.
He revealed: "Most of the children infected in Cork are teenagers and 88pc of cases have never received any dose of MMR vaccine.
"This large and rapidly spreading outbreak is a major concern. Vaccination with MMR is the only way to protect against measles. Failure to vaccinate leaves children exposed to a serious and potentially fatal disease," said Dr Kelleher.
"It exposes other children, especially babies under one year of age, to this disease. Children under one are those most likely to be liable to severe complications and possibly death."
The virus starts with a rash in the mouth that looks similar to sugar granules. Then, a red raised rash starts at the hairline and travels down the body.
Patients can have a high temperature, itchy eyes, conjunctivitis and a dry cough.
Complications can include pneumonia and ear and eye infections. Around one in 1,000 develop encephalitis -- swelling of the brain -- which can be fatal.
It is transmitted when an infected person breathes, coughs or sneezes.
The MMR vaccine is provided at 12 months of age and again at pre-school age, so babies under a year old are not protected.
Children younger than 13 who missed out on the vaccine can still get it free from their GP.
Older children can get the vaccine free but may have to pay an administration fee. The vaccine takes effect within six to 10 days.