Sierra Leonean Alhassan Kemokai was exposed to the Ebola virus while caring for his ailing mother, who later died from the disease. After becoming ill himself, he walked three miles to check himself in to the local government hospital, where after 12 days he was given the all clear. So far more than 1.300 people have died in west Africa from the Ebola outbreak. With no cure, it is still unknown why some die, but some survive