Rapid and reliable diagnosis of viral infections and tropical diseases and timely initiation of appropriate treatment are essential for their successful clinical management. This Review summarizes some basic concepts regarding the main viral infection and tropical diseases to which society is facing today and the conventional methods available for their detection. The tremendous potential offered by electrochemical affinity biosensors to address this important challenge, meeting the required demands for viral infections and tropical diseases diagnosis, is clearly stated by discussing challenges, opportunities, implementation, and application of selected examples focused on the determination of specific biomarkers of different molecular (genetic, regulatory, and functional) levels. The highlighted approaches demonstrate the use of a plethora of specific receptors and assay formats and a great diversity of attractive electrochemical approaches in this rapidly advancing and highly interesting field.