Implementation of a binational reporting protocol to identify, investigate, and report binational cases in the California border counties, 2005-2007

Background: California and Baja California seek strategies to address shared public health issues in the border region. Millions of border crossings occur every year, presenting a challenge to report infectious disease cases. A binational case is a patient or contact who traveled or resided in a neighboring state during exposure or incubation period or acquired the infection from a product, and the investigation requires collaboration of both countries. Objective: To develop a joint protocol between California-Baja California for the identification and follow-up of binational cases, and to describe binational cases identified in San Diego and Imperial counties during 2005-2007. Methods: Agreements, policies, and epidemiological surveillance systems for all jurisdictions were reviewed. Meetings were convened with local and state health authorities on both sides of the border to review surveillance and information-sharing strategies. In 2005, an informal protocol for the identification and notification of binational cases was implemented in California border counties. Results: San Diego County reported 14, 68, and 71 binational cases in 2005, 2006, and 2007, respectively. The majority (72%) were cases of Shigella, Campylobacter and Salmonella. In 2005-2007, Imperial County investigated 64 binational foodborne cases mostly Shigella, Campylobacter, and Salmonella and three binational outbreaks. Notifiable binational cases were reported by telephone and electronically to local and state epidemiologists in Baja California. Conclusions: Use of the binational case definition increased the number of cases identified by San Diego and Imperial counties. A formal implementation of a binational reporting protocol is required to enhance surveillance systems in California-Baja California.