The transmission of pathogens between well-connected countries such as Angola and Brazil is expected to increase over time due to the increase in air travel, urbanization, and climate change. This could lead to future epidemic outbreaks. The transmission of strains of the Chikungunya and Zika viruses between the two countries, for example, has already led to explosive epidemics.  However, this route of transmission is poorly uunderstood, due to the lack of suitable diagnostic tools and representative data in both regions. The extensive human mobility and synchronized vector ecologies in these countries make them important target sites for combined surveillance, which will increase our current understanding of the dynamics of the emergence and spread of unknown pathogens in these gateways. Thus, this proposal aims to elucidate the circulation and spread of arboviruses and other unknown pathogens through these gateways.