[1] Mt Auburn Hosp, Travel Med Ctr, Cambridge, MA 02138 USA
[2] Harvard Med Sch, Fac Med, Boston, MA 02115 USA
[3] Mt Auburn Hosp, Div Infect Dis & Travel Med, Cambridge, MA 02138 USA
[4] Univ Zurich, Epidemiol Biostat & Prevent Inst, WHO Collaborating Ctr Travellers Hlth, Zurich, Switzerland
[5] Univ Texas Sch Publ Hlth, Dept Epidemiol Human Genet & Environm Sci, Houston, TX USA