Ten people have now been struck down with measles in south Wales following an outbreak, it has been confirmed.

Public Health Wales says most of the people affected are teenagers or young adults living in Cardiff, Newport and Blaenau Gwent - and it has now spread to the Vale of Glamorgan too.

The trust is now urging others to get two doses of the MMR vaccine as soon as possible to prevent it spreading further.

A spokesman for Public Health Wales said: “Investigations suggest that the first few cases in the outbreak were exposed to an unknown and highly infectious case in Cardiff city centre in early February, and there has been onward transmission through secondary infections into the wider area.”

Public Health Wales says it is working with health boards and councils to contact those exposed to measles cases and arranging vaccinations.

Symptoms include fever, cough, runny nose and red eyes (conjunctivitis), and a distinctive red rash develops two to seven days after these first signs.

Anyone affected is being told they should not go to places of work, study or school, and to avoid social interactions.

Dr Gwen Lowe, consultant in communicable disease control for Public Health Wales, said: “Measles is highly infectious and the only way to prevent large outbreaks is through vaccination.

“We are expecting to see more measles cases in the coming weeks as a result of onward spread from the first group of cases. These are all linked by being in the same area in Cardiff city centre on the same day in early February.

“It is likely that there were other people exposed who also subsequently developed infectious measles and did not seek healthcare support. We have not identified the original source for the infection.

“At that time we had no known measles cases in Wales, but it is worth noting that there are significant measles outbreaks elsewhere in the UK and in other countries in Europe.

“In this particular outbreak most of the cases have been in teenagers and young adults. Health staff are therefore concentrating on identifying the settings in which these cases have been whilst infectious and making sure that their vaccination efforts are targeted towards these settings and other close contacts in the first instance.

“But as measles is currently circulating we would also urge all parents whose children have not received two doses of MMR to speak to their GP immediately and arrange for this quick, safe and effective vaccine to be given. So too should older adults who have never had measles or the MMR vaccine and work in close contact with children.”

The first dose of MMR is usually given to babies at 12 months old and the second at three years and four months of age, but it is never too late to catch up on missed doses.

The MMR vaccine is recommended by the World Health Organisation, UK Department of Health and Public Health Wales as the most effective and safe way to protect children against measles.

About one in five children with measles can experience serious complications such as ear infections, pneumonia or meningitis.

One in 10 children with measles ends up in hospital and in rare cases it can be fatal.

Parents and anyone suspecting they have measles should contact their GP or NHS Direct Wales on 0845 46 47 and alert them of the symptoms before attending any appointment.