[1] Stanford Univ, Sch Med, Div Epidemiol, Dept Hlth Res & Policy, Stanford, CA 94305 USA
[2] Stanford Univ, Dept Stat, Stanford, CA 94305 USA
[3] Stanford Univ, Dept Med, Div Infect Dis & Geog Med, Stanford, CA 94305 USA
[4] Inst Nacl Cancerol, Mexico City, DF, Mexico
[5] Univ Nacl Autonoma Mexico, Inst Invest Biomed, Mexico City 04510, DF, Mexico
[6] Ctr Dis Control & Prevent, Infect Dis Pathol, Atlanta, GA USA
[7] El Colegio Frontera Sur, Div Poblac & Salud, Chiapas, Mexico