Patients queue for anti-tuberculosis drugs at the Blue house clinic, run by medical charity Medecins Sans Frontieres (MSF), in the Mathare valley slums in Nairobi March 22, 2007. Living conditions in Africa's teeming slums have given rise to a multi-drug resistance strain of tuberculosis (MDR-TB) that kills nearly half of those who receive treatment, an aid agency said on Thursday. REUTERS/Damien Guerchois (KENYA)