[1] GSK, B-1300 Wavre, Belgium
[2] RTI Hlth Solut, F-69009 Lyon, France
[3] Royal Coll Gen Practitioners, London NW1 2FB, England
[4] British Global & Travel Hlth Assoc, London BA1 2SA, England
[5] RTI Hlth Solut, Durham, NC 27709 USA
[6] Univ Zurich, Epidemiol Biostat & Prevent Inst, WHO Collaborating Ctr TravellersHealth, CH-8001 Zurich, Switzerland
[7] Univ Texas Houston, Sch Publ Hlth, Dept Epidemiol Human Genet & Environm Sci, Houston, TX 77030 USA