¹In addition to the authors, members of the GeoSentinel Surveillance Network who contributed data are: Elizabeth Barnett, Boston University, Boston, Massachusetts, USA; Graham Brown, Royal Melbourne Hospital, Parkville, Victoria, Australia; Giampiero Carosi and Francesco Castelli, University of Brescia, Brescia, Italy; Lin Chen and Mary Wilson, Harvard University, Cambridge, Massachusetts, USA; Bradley Connor, Cornell University, New York, New York, USA; Jean Delmont and Philippe Parola, Hôpital Nord, Marseille, France; Devon Hale and Stefanie Gelman, University of Utah, Salt Lake City, Utah, USA; Elaine Jong and Jean Haulman, University of Washington, Seattle, Washington, USA; Phyllis Kozarsky and Carlos Franco, Emory University, Atlanta, Georgia, USA; Carmelo Licitra, Orlando Regional Health Center, Orlando, Florida, USA; Louis Loutan and Francois Chappuis, University of Geneva, Geneva, Switzerland; Poh Lian Lim, Tan Tock Seng Hospital, Singapore; Michael Lynch, Fresno International Travel Medical Center, Fresno, California, USA; Susan McLellan, Tulane University, New Orleans, Louisiana, USA; Prativa Pandey, CIWEC Clinic Travel Medicine Center, Kathmandu, Nepal; Cecilia Perret, Pontificia Universidad Católica de Chile, Santiago, Chile; Bradley Sack and Robin McKenzie, Johns Hopkins University, Baltimore, Maryland, USA; Hiroko Sagara, Yokohama Municipal Citizen's Hospital, Yokohama, Japan; Marc Shaw, Worldwise Travellers Health and Vaccination Centre, Auckland, New Zealand; Robert Steffan and Patricia Schlagenhauf, University of Zurich, Zurich, Switzerland; William Stauffer and Patricia Walker, University of Minnesota, Minneapolis, Minnesota, USA; and Murray Wittner, Albert Einstein School of Medicine, Bronx, New York, USA.