Media playback is unsupported on your device Media caption Another 73 cases bring the total to 693, with health officials warning still not enough children are coming forward for MMR jabs.

There as been a big jump in measles cases reported in the Swansea epidemic over the past two days, says Public Health Wales (PHW)

Another 73 cases bring the total to 693, with health officials warning still not enough children aged 10 to 17 are coming forward for MMR jabs.

Health officials have also raised concerns about the number of measles cases in Powys.

More drop-in clinics are taking place this weekend.

"We remain extremely concerned this outbreak is showing no signs of going away," said Dr Marion Lyons, of PHW.

The total number of cases in the outbreak centred on the Swansea area is now 693, up from 620 reported on Tuesday.

Analysis Swansea is vulnerable. A large campaign may have vaccinated 1,700 people, but a further 6,000 are still unprotected. Measles is an incredibly infectious and sometimes fatal disease - the end of this outbreak is not yet in sight. The surge in cases comes 15 years after confidence in the MMR jab was rocked by claims of a link with autism. That has now been completely discredited and vaccination rates have since increased. But it has left a legacy of a generation of children, across the UK, who are now going through school with low levels of protection. Across the whole of Wales and England there were 2,030 cases last year - the highest in nearly two decades. It is Swansea in 2013,. It was Merseyside in 2012. Measles outbreaks may be something we have to get used to.

More than 1,700 people received MMR jabs at special drop-in clinics in Swansea, Neath Port Talbot and Bridgend last weekend. Another 900 were vaccinated in the Swansea area last week.

However, Public Health Wales (PHW) has warned that despite those immunisations the outbreak has not been brought under control.

At least 6,000 children have still not had the MMR (measles, mumps, rubella) vaccine in the Swansea area.

Public Health Wales has also raised concerns about an increasing number of cases in Powys, with 50 reported in the Welshpool area.

'Extremely concerned'

The Swansea outbreak began last November and health officials say it shows no sign of abating.

More hospital drop-in clinics will be held in Morriston and Singleton hospitals in Swansea, Neath Port Talbot hospital and the Princess of Wales in Bridgend from 10:00 BST to 16:00 BST on Saturday.

They will target children and adolescents who did not have their scheduled MMR jabs as babies and toddlers.

PHW has said not enough children aged 10 to 17 are coming forward for the jabs, and have urged parents to get their children vaccinated through GPs.

Dr Marion Lyons, director of health protection for Public Health Wales, said: "With measles cases at almost 700, with 73 of those reported in the last two days alone, we remain extremely concerned that this outbreak is showing no signs of going away.

Measles Q&A How safe is it to take children to mainland Europe who have had two doses of the MMR vaccine? It gives 99% protection against the measles virus. What if they have had only one dose of MMR? One dose is better than none, but two doses is better than one. If you are concerned about travelling to an outbreak area you can bring forward the second MMR dose. Speak to your GP about it. What if my children are not vaccinated at all? The advice is to go to your GP and arrange for them to be immunised as soon as possible before you travel. Measles is a dangerous viral illness that can be fatal. BBC Health - Measles 'Death risk' in outbreak

"We are delighted to see parents starting to arrange vaccination for their children but the numbers simply aren't high enough to bring the outbreak under control."

She said they have particular concerns about unvaccinated children aged 10 to 14.

Public Health Wales says it is inevitable that some of those vaccinated in the past week will already be incubating measles, and vaccination will not prevent them from becoming unwell. But their illness is likely to be milder than if they had not received the vaccine.

Dr Lyons added: "Measles cannot be taken lightly because you can never tell who will go on to develop the more serious complications of pneumonia or encephalitis [brain inflammation]. MMR vaccination offers the only protection against these complications."

Meanwhile, health officials in Cardiff and Vale of Glamorgan are planning to hold drop-in vaccination clinics at Cardiff Royal Infirmary and Llandough Hospital on Saturday as a "sensible precaution" in light of the epidemic in Swansea.

Dr Tom Porter, consultant in public health medicine, said: "We have not seen a local outbreak in the Cardiff and Vale area yet but it is important that children and teenagers have both [MMR] jabs given how serious the risks are from measles."

He estimated that around 13,000 children under 19 had not had two MMR jabs and were not adequately protected.