The epidemics of severe acute respiratory syndrome (SARS), pandemic influenza (H1N1) and Middle Eastern Respiratory Syndrome (MERS-CoV) hit the world with a high pathogenic potential in recent years, providing a warning to nations of the speed with which these epidemics can move across the globe ^{1 - 3} . Everyday, nations are more internationally connected ⁴ . On February 1, 2016, for the fourth time in history, the World Health Organization (WHO) declared a public health emergency of international concern (PHEIC) to make a joint global effort to control the outbreak caused by Zika virus (ZIKV) in Latin America and the Caribbean ^{5 , 6} . These facts reiterated the need for governments and international agencies to build and strengthen the surveillance of infectious diseases at all levels, from national to international, thus facilitating the timely detection, response, and communication of disease outbreaks on a global scale ⁴ .

The International Health Regulations (IHR) recommends that countries sharing borders and having common interests consider establishing multilateral agreements ⁷ . This aims to facilitate the implementation of IHR, consolidating the direct and rapid exchange of public health information and the application of health measures at borders. This effort may prevent and/or control the international transmission of disease at the crossing point ⁷ . Land borders are physical spaces with peculiar characteristics including large historical, cultural, ethnic, economic, and social heterogeneities. In many cases, these spaces have intense population flows, which create special conditions for disease transmission ⁸ . Several studies ^{9 - 14} have indicated that these border areas possess different dynamics and patterns of occurrence of disease when compared to other areas within countries.

Brazil and the United States of America (U.S.) are countries with large extensions of land borders. Brazil’s border is 15,719 km long and is shared with ten countries, all with different health policies. The border fringe occupies an area of 2,300,000 km² (27.6% of the country), with 588 municipalities and nearly 10 million people (6% of the population) ¹⁵ . The U.S. Southern border with Mexico extends for 3,141 km, with a fringe of 100 km (62.5 miles) on each side of the border and an estimated population of 13 million people ^{16 , 17} .

Due to the long length of land borders, with intense population flows and different epidemiological and social scenarios, the vulnerability to the introduction and rapid spread of potential threats to public health is a fact that must be taken into consideration. Therefore, the development of systems and activities focusing on border epidemiological surveillance (BES) is essential both for domestic and global health security ¹⁸ . Based on the hypothesis that border surveillances must promote binational communication, an exchange of epidemiologic information in a timely and dynamic manner to improve the cross-border public health infrastructure through collaboration, this study aimed to analyze the different binational/multinational activities, programs, and structures to identify challenges and to suggest improvements of binational and/or multinational epidemiological surveillance partnerships on the borders of Brazil and the U.S.

A descriptive exploratory study about border epidemiological surveillance (BES) systems was performed in South and North America between 2013 and 2015. A total of 47 interviews at every operational level of the BES were conducted at the United States-Mexico border (US-MX border applied from February 2014 to September 2014) and Brazil (November 2014 to March 2015).

Acknowledging the vulnerability of introducing and spreading potential public health events through land borders, the International Health Regulations (IHR) recommends that countries sharing common borders should consider establishing bilateral or multilateral agreements about strengthening surveillance actions at ground crossings ⁷ .

In larger border areas, such as those of the U.S. and Brazil, there are large numbers of residents. Together with the intense population flow, this provides a favorable scenario for the occurrence and spread of communicable and noncommunicable diseases ^{8 , 27} . Ferraz et al. ²⁸ and Spradling et al. ²⁹ pointed toward different profiles of tuberculosis and acute viral hepatitis in the border regions of Brazil and the United States, respectively, when compared with States and national rates. Thus, the inclusion and prioritization of BES activities, mainly at the local and federal levels, are an important step toward consolidation of health surveillance systems reflecting the recognition of the importance of the issue by the governments.

However, as observed in this study (particularly in South America), findings show that it lacks certain protocols. These protocols, as observed at the U.S.-MX border, define the actions and communication flows between public health agencies involved with binational notifications and may support adequate responses to the occurrence of public health events. Wang et al. ³⁰ , studying vaccine-derived poliovirus (VDPV) outbreaks, noted that surveillance based on solid international collaboration and agreements with clear and well-defined paths allows for an exchange of information in a timely and dynamic manner. The contribution of such agreements was critical to avoid the VDPV outbreaks from reaching China through its land borders. The inadequacy of many surveillance indicators (lack of opportunity for the exchange of epidemiological information, quality of the epidemiological information, reciprocity, feedback, and incompleteness of information) may be related to the informality of the BES operational articulation.

BES systems in North and South America have taken important steps toward systematizing their activities. Both international borders are defining their priorities and actions in these regions together with stakeholders and partners of the neighboring countries. North American countries have developed and distributed a document detailing the step-by-step operational flow of information and actions because these countries place a higher priority on their actions. BES services that have developed and implemented such protocols and plans result in more clear and efficient conduction, evaluation, and review of operational procedures. In addition, the activities are not linked to specific individuals, but are rather institutionalized, allowing the continuity of standard procedures and minimizing disruptions to required actions.

A lack of human, technical, and financial resources were major obstacles in Brazil and Mexico. Scarcity of primarily financial resources to hire technicians weakens the systems of these two countries. The lack of technicians and high personnel turnover at the jurisdiction level creates a burden on the technical staff, affecting the necessary epidemiological actions. In this respect, Bruniera-Oliveira et al. ²¹ evaluated Brazil’s rotavirus epidemiological surveillance, noting that the limited number of technicalities and high turnover caused a delay in the process, transfer and response of the rotavirus surveillance.

The need for a greater investment in human, technical, and financial resources was unanimous by respondents in both of the studied areas. It is possible that many of the process difficulties, particularly information exchange, are due to structural differences between the countries involved. While, in Brazil there is a system that facilitates mechanisms to carry out information exchange quickly and confidentially, other countries are using unsafe means for information exchange. This structural discrepancy generates resistance, especially when health services are dealing with personal information. Furthermore, there are mechanism incompatibilities, such as differences in software versions used or even lack of such mechanisms. Therefore, countries with available resources should seek ways to standardize communication mechanisms ²⁶ .

Particular attention should be given to laboratories, which provide support for border surveillance. For most of the infectious diseases of public health concern, laboratory confirmation is essential for planning and triggering the control and prevention actions. Thus, the organization of a laboratory network able to meet demands of the border areas would increase sensitivity, opportunity, and system specificity ³¹ . In North America, due to the systems developed at the borders, such as the Border Infectious Disease Surveillance (BIDS), there was a substantial reduction in disparities with surveillance capabilities in incompatibility of used case definitions. This resulted in increased diagnostic capacity and laboratory capability in the region ⁹ .

In Brazil, the Border Laboratories Network can be considered innovative as it seeks to reduce the differences in laboratory capacity between countries. However, despite what has been developed so far, significant obstacles were identified, such as a lack of support from federal laboratories and no standardization of techniques among countries. This hindered comparisons and the planning of binational actions. A study about the occurrence of public health emergencies in Brazil proved that, in the border areas, laboratory confirmation remains low for suspected cases ²¹ . This lack of diagnosis can be attributed to the high testing demand that these laboratories have, which requires additional investment for its expansion and an increase of capacity to become a robust border network. Although one of the response pillars to the Ebola outbreak in West Africa has been the laboratory support, the lack of capacity during the early stages of the epidemic was undoubtedly a factor that contributed to Ebola’s rapid expansion, reinforcing the idea of consolidating a prepared network to respond to any type of threat ^{32 , 33} . Such difficulties in the BES development, including laboratory services, may have contributed to a weak capacity to detect and respond in a timely manner to public health events, as observed for the Brazilian international border municipalities ³⁴ . The analysis of their capacity to report infectious diseases with a potential to generate an epidemic demonstrated a very low proportion (16,6%) of cases of these diseases being reported in a timely manner (< 24 hours - as established nationally).

The political organization of different countries for the entry and movement of people through borders are relevant factors in the comparison of surveillance systems and in the design of health systems for the border regions. The Treaty of Asunción, which gave rise to MERCOSUR, establishes that the States’ parties have the freedom of movement for people, goods, and services among them ³⁵ . Hence, the Brazilian Southern Border Arc has an extremely high daily porosity for people entry and exit, once the crossing between countries can be taken without any impediment. As evidenced by the research, there are numerous points of entry, where there are no checkpoints, such as health inspection points or customs. On the other hand, in North America, in addition to the physical barriers along the border, all entry points are controlled by U.S. Customs and Border Protection (CBP). This agency first screens incoming international travelers with the CDC and has the power to detain for the enforcement of isolation and quarantine of individuals with any signs and/or symptoms of infectious diseases ³⁶ . The presence of such agencies as the CBP plays an important role in the containment of infectious diseases entering the United States. Countries that applied travel restrictions on their borders during the epidemic of the influenza virus A (H1N1) observed that both the restriction and the isolation and quarantine of the cases played an important contribution in the delay of the virus in their countries ^{37 , 38} .

The lack of a screening process at the border crossing points temporarily makes the detection of potential suspect cases very passive, dependent on volunteers seeking health assistance. The receiving health facility of a suspected case must be prepared to provide the initial care to isolate the case when necessary or make the transport to the place of isolation. They must then communicate in a timely manner with the respective authorities in the neighboring country to begin the binational investigation. Moreover, all health facilities in the border region, including laboratories, must be notified about the possible suspect cases. An online system for binational notification would be the tool of choice. All levels involved in the response could then input, search, and follow up in real time on all the epidemiological information of cases, thus creating increased transparency and dynamism to the response process. Inside this network, an important movement should be made to bring international organizations closer, such as PAHO and multilateral mechanisms, as MERCOSUR and UNASUR. These structures and mechanisms should have important tools that have been created for international health dialogue so they can act as front ambassadors to stalemates when an urgent international response is required. Forums and mechanisms created by these agencies are important health authorities of the participating countries. Due to the previous meetings, they already have affinities, which facilitate and streamline the dialogue and target the most controversial issues.

One of the limitations of this study was the voluntary participation, which made some of the invited stakeholders/key coordinators not available to answer the survey. Another limitation was the financial aspect, which restricted the field visit to just one point of entry into South America. Specifically, in the South Arc, obtaining responses from Paraguayan technicians would have enhanced and contributed much to the technical discussion. However, despite numerous contacts and invitations, this did not materialize. This limitation has highlighted the lack of multinational mechanisms that could facilitate and would promote dialogue with BES structures.

Taking from the results observed in this study, the following concluding points can be highlighted: i) availability of a protocol to North American borders; international borders are defining their priorities and actions at these regions together with stakeholders and partners from neighboring countries and the existence of border laboratories; ii) because this is a study, among the few, focused on border epidemiological surveillance in the Americas’ Southern Cone countries, this research has raised questions about borders that require special attention to delineate and help the flow of work processes; iii) the continuous, systematic development of surveillance systems at the borders will provide more effectiveness to the implementation of actions and responses; thus, countries can improve their mechanisms to respond in future outbreaks; iv) considering the external validity of this study, the results achieved do not necessarily apply to the reality of other borders; however, the instrument used in this research can be adapted to be used in studies that deal with border surveillance in other parts of the world.