A first group of volunteers from Britain's state National Health Service have left for Sierra Leone to join the Ebola epidemic fightback.

More than 30 NHS workers flew out of London Heathrow Airport and were due to arrive in the capital Freetown on Sunday for a week of training before moving to British-built treatment centres around the west African country.

The group includes doctors, nurses, clinicians, psychiatrists and emergency medicine consultants.

Doctor James Lavers, 37, an intensive care registrar from Bangor in northwest Wales, said: "This could be the biggest medical disaster of my lifetime, killing hundreds of thousands of people in the region. To prevent this from happening and save vast numbers of lives, large-scale intervention has to happen now."

The volunteers have gone through nine days of intensive training at a specialist Ministry of Defence unit in northern England, which has a replica treatment centre.

More than 1,000 NHS workers have put their names forward and more teams of British volunteers are due to go out to Sierra Leone over the coming weeks.

More than 5,000 people have died in the west African Ebola outbreak and more than 15,000 have been infected.

Recent data has shown a decline in cases in Liberia, the worst-hit country, and Guinea, but last week, 533 new cases were reported in Sierra Leone - the highest weekly tally since the epidemic began in that country.

Australia, New Zealand, Cuba, Norway and Denmark have committed to providing health workers to staff the British treatment centres alongside the NHS volunteers.