Ebola 'in decline' but recovery 'a long and bumpy tail'

West Africa's Ebola crisis is 'in decline' but is likely to last until the end of 2015, says a leading researcher who helped to discover the virus.

Peter Piot, Director of the London School of Hygiene and Tropical Medicine, and a member of the team of scientists that discovered Ebola in 1976, has just returned from Sierra Leone.

He told the BBC that he was encouraged by progress there and by the promise of new anti-viral therapies.

He also warned that vaccines would take time to develop and would require a 'sustained effort for the rest of 2015'.

Professor Piot spoke to the BBC's Nkem Ifejika.