Twelve case of probable measles and four confirmed cases have been diagnosed in Swansea, Port Talbot and Haverfordwest.
Two people were taken to hospital, but have now been discharged.
– Dr Jorg Hoffmann, Public Health Wales
Measles is a highly infectious disease that can cause complications including pneumonia, meningitis and encephalitis, particularly in children under five years of age, those with weakened immune systems and children with a poor diet.
Parents can easily protect their children by having them immunised with the MMR vaccine. After completing a two-dose course of MMR, 99 per cent of children will be protected against measles.
The only way to prevent outbreaks of measles is to ensure that at least 95 per cent of children in Wales have received two doses of the MMR vaccine.
It's suspected that the cases are linked with people who stayed at a holiday camp in South West England during the second half of October.
Letters are being sent to schools in the affected areas, and a vaccination catch up session is also being arranged at Pentrehafod Comprehensive School, Swansea.