Gerard J. B. Sonder, Jim E. van Steenbergen, Lian P. M. J. Bovee, Roel A. Coutinho, and Anneke van den Hoek are with the GG&GD, Department of Infectious Diseases, Municipal Health Service, Amsterdam, the Netherlands. Paul G. H. Peerbooms is with GG&GD Municipal Health Laboratory, Amsterdam. Dr. Sonder also is with LCR, National Coordination Center for Travelers Health Advice, Amsterdam. Dr. van Steenbergen also is with LCI, Coordination Communicable Disease Control, Utrecht, the Netherlands. Dr. Coutinho...