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London doctor treating Ebola victims in Sierra Leone

5 August 2014 Last updated at 22:11 BST

A doctor from King's College in London has been treating patients with the deadly Ebola virus in Sierra Leone.

Dr Oliver Johnson admits there are risks that he could catch the virus. So far, a US doctor has been infected in Liberia.

Since February, nearly 900 people have died from the disease which is affecting four west African countries - Guinea, Liberia, Sierra Leone and Nigeria.