- 2 updates
There have been measles cases reported at two primary schools, a further education college, and a nursery - in addition to cases at Cwmtawe School in Pontardawe.
Public Health Wales says it wants to remind parents that children need two doses of MMR for the maximum 99 per cent protection against measles.
The virus is very contagious, can cause serious complications and even be fatal.
The symptoms of measles include: fever, fatigue, runny nose, conjunctivitis, a distinctive red rash.
Public Health Wales is urging anyone who thinks they or their children has the symptoms should contact their GP or NHS Direct Wales on 0845 46 47.
Public health officials are warning that the number of measles cases has risen to 14, after an outbreak earlier this year.
There are now 13 cases linked to Cwmtawe School in Pontardawe, and a case of suspected measles with no apparent links to the school, at a nursery in the Swansea area.
Public Health Wales says there is "potential for the outbreak to spread quickly", unless children who have not received two doses of the MMR are vaccinated urgently.
Two weeks ago, vaccination clinics were held at the secondary school in Pontardawe, after the first case was confirmed.
The last outbreak, centred on Swansea and Neath Port Talbot, was declared over in July, having started last November.
It resulted in more than 1,200 cases.