Until 20 years ago measles had been effectively wiped out in Britain.
But now it is back and is officially classed as an epidemic in South Wales.
This is modern healthcare turned upside down.
Fifteen years ago the offices of the South Wales Evening Post were buzzing with controversy.
A doctor had claimed the MMR vaccine caused the behavioural condition autism in children.
Suddenly parents were refusing to vaccinate their children against a killer.
But 15 years later doctors are still furious that an atmosphere was created which led to them being portrayed as the bad guys.
Al Jazeera's Laurence Lee reports from Swansea, South Wales.