[1] Emory Univ, Sch Med, Div Infect Dis, TravelWell Clin, Atlanta, GA 30308 USA
[2] Hosp Infantil Mexico Dr Federico Gomez, Federico Gomez, Mexico
[3] Inst Publ Hlth, Oakland, CA USA
[4] Univ Nacl Autonoma Mexico, Fac Med, Unidad Med Expt, Mexico City 04510, DF, Mexico