Medical experts say there's been a four-fold rise in the number of Welsh cases of measles this year, compared to the previous 12 months.
From January to June there were 61 cases.
Public Health Wales says raising MMR vaccination rates is the key to tackling the problem.
Incidences of whooping cough were also up.
More top news
In the second of our special series Welsh education: Making the grade? we visited Bishop Hedley High in Merthyr Tydfil.
More wintry showers will continue overnight and a yellow warning of ice has been issued for central and eastern parts.
Swansea Dry Dock says it's missed out on a number of contracts to dismantle warships because they've gone elsewhere.