The U.S.-Mexico border infectious disease surveillance project: establishing binational border surveillance - Research

Emerging Infectious Diseases, Jan, 2003 by Michelle Weinberg, Stephen Waterman, Carlos Alvarez Lucas, Veronica Carrion Falcon, Pablo Kuri Morales, Luis Anaya Lopez, Chris Peter, Alejandro Escobar Gutierrez, Ernesto Ramirez Gonzalez, Ana Flisser, Ralph Bryan, Enrique Navarro Valle, Alfonso Rodriguez, Gerardo Alvarez Hernandez, Cecilia Rosales, Javier Arias Ortiz, Michael Landen, Hugo Vilchis, Julie Rawlings, Francisco Lopez Leal, Luis Ortega, Elaine Flagg, Roberto Tapia Conyer, Martin Cetron

In 1997, the Centers for Disease Control and Prevention, the Mexican Secretariat of Health, and border health officials began the development of the Border Infectious Disease Surveillance (BIDS) project, a surveillance system for infectious diseases along the U.S.-Mexico border. During a 3-year period, a binational team implemented an active, sentinel surveillance system for hepatitis and febrile exanthems at 13 clinical sites. The network developed surveillance protocols, trained nine surveillance coordinators, established serologic testing at four Mexican border laboratories, and created agreements for data sharing and notification of selected diseases and outbreaks. BIDS facilitated investigations of dengue fever in Texas-Tamaulipas and measles in California-Baja California. BIDS demonstrates that a binational effort with local, state, and federal participation can create a regional surveillance system that crosses an international border. Reducing administrative, infrastructure, and political barriers to cross-border public health collaboration will enhance the effectiveness of disease prevention projects such as BIDS.

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The 2,000-mile U.S.-Mexico border is one of the world's busiest international boundaries. An estimated 320 million people cross the northbound border legally every year (1). The U.S.-Mexico border is a unique region where the geopolitical boundary does not inhibit social and economic interactions nor the transmission of infectious diseases among residents on each side of the border. Some border cities (such as El Paso and Ciudad Juarez) are separated by a short distance and serve as one large metropolitan area for the local community (Figure 1). From an epidemiologic perspective, the border population must be considered as one, rather than different populations on two sides of a border; pathogens do not recognize the geopolitical boundaries established by human beings. The border region has a population of approximately 11 million people (2), many of whom cross the border daily to work, shop, attend school, seek medical care, or visit family and friends (3,4). The border population also includes persons who pass transiently through the region and others who come the area to work in maquilas, the border factories. The region has experienced tremendous population growth. During 1993-1997, the U.S. border population grew by 1.8% annually, more than double the national U.S. average of 0.8%, while the Mexican border population has grown by 4.3% per year, almost three times the national Mexican annual growth rate of 1.6% (2,5). Population growth has been spurred by increased economic opportunities after the North American Free Trade Agreement was implemented in 1994. Currently, an estimated 3,300 maquilas, employing >1 million workers, are located along the border (6,7). The proliferation of border factories has generated a wave of internal migration of persons from other regions of Mexico and Central America toward the border (8).

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From Mexico's perspective, the border encompasses some of the country's most economically prosperous states. In contrast, the U.S. border region is among the poorest areas in the United States, with >30% of families living at or below the poverty level (8). Along the Texas border, an estimated 350,000 or more people live in 1,450 unincorporated areas known as colonias, which lack adequate sanitation infrastructure (8).

The large population movement, limited public health infrastructure, and poor environmental conditions contribute to increased incidence of certain infectious diseases (8-11) Analysis of data from the U.S. National Notifiable Diseases Surveillance System for 1990 through 1998 showed increased risks for certain foodborne, waterborne, and vaccine-preventable diseases in U.S. counties within 100 kilometers of the border, compared with nonborder states. These data show a two- to fourfold greater incidence of hepatitis A, measles, rubella, shigellosis, and rabies and an eightfold greater incidence of brucellosis in border counties than in nonborder states (11). Studies have identified the importance of crossborder movement in the transmission of various diseases, including hepatitis A (12,13), tuberculosis (14-18), shigellosis (19), syphilis (20), Mycobacterium boris infection (21), and brucellosis (22,23).

Despite the high prevalence of infectious diseases and increasing movement of people across the borders, no surveillance system had been established to assess the border population as a geographic unit. Gaining an accurate picture of public health needs was limited by the following factors. First, the surveillance case definitions used for public health reporting in Mexico and the United States are different. Also, laboratory confirmation is often unavailable in the Mexican border states, and therefore reported cases of infectious diseases are defined primarily by clinical findings. In contrast, for the many notifiable diseases in the United States, laboratory confirmation is required, and U.S. surveillance is heavily based on laboratory reporting. This system likely underestimates the true incidence rates. In the past, the two countries have exchanged limited border surveillance data. However, these differences diminish the usefulness of national surveillance data for developing a comprehensive, regional understanding of infectious disease epidemiology in the border areas. A consistent binational perspective is essential to effectively control and prevent the transmission of infectious diseases that move easily through the geopolitical boundary.

The Border Infectious Disease Surveillance (BIDS) project was designed to bridge this surveillance gap by forming partnerships among institutions in both countries serving the region and bringing together each country's complementary experiences in syndromic and laboratory-based surveillance. This report describes the establishment of a binational surveillance system for hepatitis and febrile exanthems along the U.S.-Mexico border.

Project Mandate

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.

Site Selection

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.