Parents in Wales are again warned to make sure their children have the MMR jab the number of cases tops 200.
Health chiefs fear one of the biggest measles outbreaks in Wales will become fatal after figures showed 207 people are suffering from the virus.
Several people have been treated in intensive care units after the worst outbreak of the disease in years.
The National Public Health Service (NPHS) is urging parents to ensure their children are vaccinated.
Dr Marion Lyons of the NPHS said: "Any child who is overdue for vaccination is at risk."
The mid and west Wales areas have seen 147 cases, with 23 people admitted to hospital.
Eighty-nine of the cases in mid and west Wales are linked to four outbreaks in south Pembrokeshire, Llanelli, Burry Port and Neath Port Talbot areas, while the others are sporadic cases across seven county areas.
We fear it is only a matter of time before someone dies
Dr Marion Lyons NPHS
In Llandudno, there are 53 cases with two people taken to hospital, linked to outbreaks in two schools, Ysgol Ffordd Dyffryn and Ysgol John Bright.
Five of the seven in south east Wales cases have family links to the mid and west Wales cases while the others are sporadic.
Dr Marion Lyons, head of the health protection teams for the NPHS, said: "For as long as there are children who do not receive their MMR vaccinations, there is the potential for people to become ill with measles.
"With so many cases in the community, any child who is overdue for vaccination is at risk and we are urging parents who have still not arranged immunisation for their children to act immediately.
"MMR is a safe vaccine that protects children from the most severe viral rash illness of childhood.
The illness is associated with a blotchy rash which spreads down from the face
"There is strong evidence that worldwide, as many as one in 500 children who catch measles will die, and another one in 500 will suffer permanent brain damage.
"With 26 people now admitted to hospital because of these measles outbreaks - some of them having spent time in intensive care units - we fear it is only a matter of time before someone dies or is left permanently affected by measles.
"The people most at risk of catching measles are children of school age or children between the ages of one and four who are not up-to-date with their vaccinations.
"Although we are seeing cases of measles in adults, it is rare for anyone born before 1970 to catch measles."
The NPHS said many people who catch measles will have a fever, cough, red eyes, and blocked nose and feel generally unwell. The blotchy rash appears a few days later beginning on the face and spreading downwards to the rest of the body over several days.
Typically, the organisation added, people will be infectious from the day before their first symptoms until four to five days after the appearance of the rash.
Dr Lyons explained: "If your child is unwell and you suspect it is measles, you should contact your GP. Your child should not attend school or nursery for five days after the rash starts.
"After completing a two-dose course of the MMR vaccine - which also offers protection against mumps and rubella - 99% of children will be protected against measles."
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