Existing syndromic surveillance systems include the CDC's drop-in surveillance systems, 8 Early Notification of Community-based Epidemics (ESSENCE), 10,18 the Lightweight Epidemiology Advanced Detection and Emergency Response System (LEADERS), 19 the Rapid Syndrome Validation Project (RSVP), 20 and the eight systems discussed by Lober et al. 11 Lober et al. summarized desirable characteristics of syndromic surveillance systems and analyzed the extent to which systems that were in existence in 2001 had those characteristics. 11 A limitation of most systems (e.g., ESSENCE, 10 Children's Hospital in Boston, 11 University of Washington 11 ) was batch transfer of data, which may delay detection by as long as the time interval (periodicity) between batch transfers. For example, a surveillance system with daily batch transfer may delay by one day the detection of an outbreak.