Why do so many African leaders die in office

The funeral of Ghana's John Atta Mills [Photo: AP]

It's rare for the leader of a country to die in office. Since 2008, it's happened 13 times worldwide - but 10 of those leaders have been African. Why is it so much more common in this one continent?

Large crowds carrying candles ran alongside the hearse carrying the body of Meles Zenawi, as it made its way through Addis Ababa, on Tuesday. He had died, aged 57, after a long illness.