[1] Univ Verona, Unit Epidemiol & Med Stat, Verona, Italy
[2] Mekelle Univ, Sch Publ Hlth, Mekelle, Ethiopia
[3] Univ Pavia, Dept Publ Hlth Expt & Forens Med, Biostat & Clin Epidemiol Unit, I-27100 Pavia, Italy
[4] Stellenbosch Univ, Fac Med & Hlth Sci, Cape Town, South Africa
[5] Johns Hopkins Bloomberg Sch Publ Hlth, Dept Int Hlth, Baltimore, MD 21205 USA