[1] Ctr Dis Control & Prevent, Atlanta, GA 30333 USA
[2] Toronto Hosp, Toronto, ON M5T 2S8, Canada
[3] Canadian Int Water & Energy Consultants, Clin Travel Med Ctr, Kathmandu, Nepal
[4] Univ Zurich, CH-8006 Zurich, Switzerland
[5] WHO, Collaborating Ctr Travelers Hlth, Zurich, Switzerland