There are now more than 300 cases of measles across South West Wales.
Officials have warned that it is only a matter of time before permanent damage is done, or a child dies.
One mother has told ITV Cymru Wales she became seriously concerned when two of her children fell ill as part of the outbreak.
She's now calling on parents to have their children vaccinated, as Kevin Ashford reports.
Fresh measles cases have been reported in Powys and Cardiff. A public health expert warned tens of thousands of children could be at risk.
Public Health Wales has information and advice on measles - a highly-infectious viral illness which can have life-threatening complications.