[1] Loyola Univ, Stritch Sch Med, Dept Prevent Med & Epidemiol, Maywood, IL 60153 USA
[2] Univ Coll Ibadan Hosp, Dept Pediat, Ibadan, Nigeria
[3] Univ Autonoma Madrid, Dept Med Prevent & Salud Publ, Fac Med, E-28049 Madrid, Spain
[4] Univ W Indies, Res Inst Trop Med, Kingston 7, Jamaica
[5] Ist Super Sanita, Epidemiol & Biostat Lab, I-00161 Rome, Italy
[6] Dalhousie Univ, Fac Med, Dept Community Hlth & Epidemiol, Halifax, NS, Canada
[7] Univ Kuopio, Dept Publ Hlth & Gen Practice, FIN-70211 Kuopio, Finland
[8] UCL, Sch Med, Dept Epidemiol & Publ Hlth, London W1N 8AA, England
[9] Univ Hosp, Dept Med, Umea, Sweden
[10] Robert Koch Inst, Berlin, Germany