[1] Univ London Imperial Coll Sci Technol & Med, MRC PHE Ctr Environm & Hlth, Sch Publ Hlth, Norfolk Pl, London W2 1PG, England
[2] Harvard Univ, Dept Emergency Med, Sch Med, Boston, MA 02115 USA
[3] Groote Schuur Hosp, Dept Med, ZA-7925 Cape Town, South Africa
[4] Univ Cape Town, ZA-7925 Cape Town, South Africa
[5] Univ London London Sch Hyg & Trop Med, Fac Epidemiol & Populat Sci, Dept Noncommunicable Dis Epidemiol, London WC1E 7HT, England