Smallpox: Why do USA and Russia hang on to stockpiles?
The World Health Organisation is debating whether to preserve or destroy the last known stockpiles of smallpox, which are held by Russia and the USA.
Giles Dilnot explains the background before Professor Gareth Williams from Bristol University claims there is no scientific or medical reason to retain any stock of it.
Former ambassador Sir Christopher Meyer backs the calls to get rid of it, but explains why the US may want to hang on to its supply.