In June 1997, the United States–Mexico Border Health Association and the U.S. Council of State and Territorial Epidemiologists passed resolutions to support surveillance for infectious diseases and emerging infectious diseases along the U.S.-Mexico border (24,25). The Centers for Disease Control and Prevention (CDC) and the Mexican Secretariat of Health spearheaded efforts to initiate the project and formalized an agreement to establish BIDS through a memorandum of cooperation in epidemiology. A binational team of local, state, and federal epidemiologists, laboratory scientists, and public health officials met to organize and define project objectives. Decisions were made by consensus among the participants.

The team selected four sister city groups that had previously collaborated on binational projects (Figure 2). Local and state health departments identified one or more clinical facilities in each city. The U.S. institutions are four primary-care clinics and three tertiary care hospitals. The Mexican sites comprise two general hospitals and four primary-care clinics. The primary-care institutions service 10,000–20,000 acute-care visits per site annually, while the hospitals service 23,000–51,000 acute-care visits per site annually.

After extensive discussions about local and national disease priorities, the team agreed on active sentinel surveillance for hepatitis and febrile exanthem syndromes. A standard protocol of laboratory testing is performed for specimens from patients who fulfill the clinical entry criteria (Table 1). Patients with acute hepatitis are tested at local laboratories for hepatitis A, B, and C. Depending on the initial results, specimens are tested at CDC for hepatitis D and E, and confirmatory testing for hepatitis C is performed. Patients with febrile exanthems are tested locally for measles and rubella. If these tests are negative, the specimens are tested at a state or national reference laboratory for rickettsiae, ehrlichiae, and, in selected areas, dengue virus (DENV).

Many diseases selected for BIDS surveillance have well-defined preventive strategies, including vaccination. In Mexico, measles is targeted for elimination, and rubella vaccination was incorporated into the national vaccination program in 1998 (26). In the United States., rubella outbreaks have occurred among Hispanic immigrants who were not previously immunized (27–30). The south Texas border also represents an important zone for transmission of DENV (31–33) and typhus (34–36). In the United States, routine vaccination for hepatitis A was recently recommended for children in most of the U.S.-Mexico border region (37). Since laboratory confirmation was not readily available in Mexico, most acute hepatitis was assumed to be acute hepatitis A; however, the extent of hepatitis B and hepatitis C infection was unknown. Syndromic surveillance facilitated the monitoring of diseases targeted for elimination as well as identification of emerging infectious diseases, such as hepatitis E and ehrlichliosis, which have not been previously well studied along the border. The selection of these surveillance conditions was influenced by the need to establish laboratory infrastructure in Mexico; the hepatitis and febrile exanthem testing protocols involve serologic assays with similar equipment and assay techniques. From the practical perspective, sentinel surveillance enabled clinics in several border cities to participate at a reasonable cost. Active surveillance was selected to enhance existing passive surveillance activities in both countries, and, rather than creating a parallel structure, all activities were integrated into state and national reporting systems.

The group formed an executive committee and three subcommittees (epidemiology, laboratory, and communications). Nine sentinel site surveillance coordinators, who report to a local health department epidemiologist and a state-based epidemiologist, were hired and trained. The sentinel site coordinators are responsible for interviewing patients, completing data entry, and handling logistical issues such as specimen shipping and tracking. Considerable training was provided for border laboratory personnel. Only one of the Mexican border laboratories had experience performing serologic testing for hepatitis viruses, and none were experienced with testing for measles or rubella viruses. Laboratory scientists from Instituto de Diagnóstico y Referencias Epidemiológicas, Mexico City, received training in testing methods for rickettsiae and ehrlichiae.

Improving binational communication systems was critical to project success. In addition to language and cultural barriers, a large gap exists in communications infrastructure between the United States and Mexico. Many Mexican local and state health departments use combined telephone and fax lines and have no Internet access; regularly scheduled conference calls are a principal mechanism for communication. Borderwide meetings are held annually and sister city groups have regional meetings. A binational team of epidemiologists, laboratory scientists, and a representative from the El Paso Field Office of the Pan American Health Organization conducts site visits and evaluations.

The movement of equipment, supplies, specimens, and financial resources between the two countries has been difficult and labor-intensive. Logistical issues include the challenges of moving laboratory equipment and supplies into Mexico and specimens across the border into the United States. Several U.S. and Mexican agencies regulate these cross-border movements. Although regulations are established at a federal level, they are often subject to local interpretation. As a result, the BIDS participants work closely with local agencies in their state.

In the past, sharing of surveillance data has been constrained due to differences in political systems, limited forums in which to share information, and poor comparability of the data. Two protocols were developed to improve information sharing. The first describes the flow of information process in each country. Although the Mexican health sector is currently undergoing decentralization, officials from the federal Mexican Secretariat of Health continue to play the major role in reviewing, analyzing, and approving data before information is shared with U.S. counterparts and CDC. In contrast, U.S. local and state data can be shared without federal approval. The second protocol establishes conditions for urgent notification of sister city sites of outbreaks and cases of selected diseases, such as measles. Urgent notification also occurs for cases of binational public health importance, such as a case of hepatitis A in a person who works as a food handler on either side of the border. In the routine disease surveillance systems of both the United States and Mexico, a reportable condition diagnosed at a medical facility on one side of the border, in a patient who lives on the opposite side of the border, may not be included in routine disease reporting, and this information is not usually provided to the neighboring health officials. Data about these binational cases have not been traditionally captured in either country’s reporting system. Therefore, binational case definitions were developed for BIDS participants (Table 2).

The project timeline is shown in Table 3. Data collection began in late 1999, and data are currently being analyzed. As of mid-2002, the network had identified 867 persons with hepatitis and hepatitis syndrome (369 in the United States and 498 in Mexico) and 421 persons with a febrile exanthem syndrome (243 in the United States and 178 in Mexico). The project has enhanced local reporting of these conditions. In 2000, BIDS surveillance data from the sentinel site in Tijuana, Baja California, identified 300% more cases of laboratory-confirmed hepatitis A than would have been expected. All hepatitis A cases identified at the San Diego site were binational and were reported to the sister city health department in Tijuana.

The BIDS network has prompted valuable data exchange as well. In 2000, California and Baja California shared important information about measles in California and rubella in both states. The Baja California Health Department used BIDS surveillance data to conduct epidemiologic follow-up and targeted vaccination as part of their efforts to eliminate measles and reduce rubella. In 1999, the Mexican Secretariat of Health, CDC, and health officials from Texas and Tamaulipas conducted the first binational investigation of an outbreak of dengue fever (38).

Consolidation, evaluation, and expansion of BIDS will take place in 2002–2003. The project, which began at 9 sites, has expanded to 13 sites. Continuing efforts will focus on incorporating six new clinical sites and three new border cities (Figure 2). With sufficient expansion, BIDS may be able to calculate population-based incidence rates for selected infectious diseases in some border areas. However, BIDS will continue to deal with the complexities of conducting surveillance among mobile populations and obtaining accurate denominator information for the border region.

Although activities focused initially on hepatitis and febrile exanthems, the project is sufficiently flexible to incorporate other syndromes and diseases, including West Nile virus and infectious agents that could be used in bioterrorism events. BIDS continues to improve communications systems and support mechanisms for information exchange.

The BIDS project demonstrates that the development of a binational regional surveillance system for one of the world’s busiest geographic boundaries is feasible. Success is highly dependent on extensive U.S. and Mexican local and state involvement; maintaining a balance among the competing priorities of this diverse group of participants continues to be one of the project's greatest challenges. A high level of participation among the group is an essential ingredient in creating a binational, locally-relevant agenda and enhancing long-term project sustainability. The BIDS surveillance system has required flexibility to incorporate local and state reporting requirements, while maintaining sufficient standardization of case definitions, data, and laboratory testing procedures. Dedicated coordination at the federal level of both countries has been essential. Maintaining federal political commitment and funding for the 3-year development and implementation period has been and continues to be critical.

BIDS promotes communication and cooperation through border-wide meetings and the binational subcommittees. The border sister city meetings provide a forum for exchange of ideas and discussion of issues of binational importance, thus strengthening cross-border relationships among counterpart epidemiologists and laboratory staff. Many logistical problems require local solutions best handled by the sister cities working together. Effective problem solving requires coordination and optimal communication among participants. However, this level of effectiveness will not be achieved in the border region until the infrastructure barriers are overcome, including substantial improvements in access to telephones, fax machines, computers, the Internet, and satellite teleconferencing.

BIDS continues to face major obstacles in the movement of equipment, supplies, specimens, and financial resources across borders. These activities are cumbersome and time consuming for all project participants. Accords between the United States and Mexico should be developed to promote cooperation in public health and facilitate sharing of human and other resources and the moving of laboratory specimens across the border; these agreements would substantially enhance border health activities and benefit both countries. The states of Arizona and Sonora cooperated successfully in establishing a shared border health facility in Nogales, Sonora. This state-based model could be replicated in other areas of the border and reinforced with federal policies. To further enhance federal support, we suggest that a joint border field station be established by CDC, the Mexican General Directorate of Epidemiology, and the Instituto de Diagnóstico y Referencias Epidemiológicas.

The mandates from the United States–Mexico Border Health Association and the Council of State and Territorial Epidemiologists served as an initiation point for project activities but did not anticipate the need for additional federal-level agreements for data exchange. The BIDS group has drafted guidelines for conducting a binational outbreak investigation and will be implementing these as opportunities arise. Ongoing data collection will enable better characterization of binational cases. However, formal agreements at high levels of government are needed to authorize and endorse the timely binational exchange of epidemiologic and laboratory information about important infectious disease outbreaks and cases that occur along the border at BIDS sites and sites that are not currently part of the BIDS network.

Political changes at the local, state, and federal levels in Mexico frequently lead to changes in public health personnel, resulting in an ongoing need to train and incorporate new personnel into the project; this reality has highlighted the importance of institutionalizing any binational project through high-level formal agreements between the two countries. Weathering political changes is a challenge to infrastructure-building projects, like BIDS, which require several years of investment until tangible results, such as data are available.

To achieve the goal of building border epidemiology and laboratory capacity, BIDS established a system that built on existing strengths in syndromic and laboratory surveillance. The enhancement of border laboratory infrastructure at the Mexican sites was a major benefit. Additional support is essential, including stable funding for laboratory supplies and training courses, ranging from laboratory techniques to preventive maintenance of laboratory equipment; implementation of standardized quality control and quality assurance guidelines, such as a voluntary blinded proficiency testing program for selected tests; and a telephone consultation service with a toll-free telephone number to help staff address the problems.

Syndromic surveillance for hepatitis and febrile exanthems will allow us to estimate the magnitude of public health problems along the border, for example, acute hepatitis B and hepatitis C; determine the geographic distribution of diseases, such as typhus, ehrlichiosis, and dengue; detect outbreaks; evaluate control measures, such as immunization efforts to prevent measles, rubella, and hepatitis A and the reduction of breeding sites for mosquitoes that transmit dengue; and monitor emerging infections, such as hepatitis E, and generate hypotheses about these diseases that can be further studied. Systematic collection of surveillance data on binational cases will also better define the contribution of mobile populations to disease transmission.

As a model for true binational cooperation along the border, BIDS is a starting point from which a comprehensive infrastructure can be developed to accurately assess the health status of border residents and other migrants who come through the area. Ultimately, data provided by BIDS will be useful in the development of more effective prevention and control strategies for infectious diseases in this unique region.