Epidemic outbreaks related to yellow fever viruses, added to the climate of fear resulting from the COVID-19 pandemic, raise a spectrum of concern and need for preparation in different research, epidemiology, and health groups. This question refers to conditions of: molecular analysis of the virus, its dissemination potential, vectors, mutational speed rate, evolutionary potential, and potential damage to individuals and populations. With regard to the yellow fever virus, such questions are even more pressing due to its successful history of colonization in America, originating from regions of Africa, and becoming endemic in both continents. Through the study of viral history and epidemiology, we seek to establish bases that allow us to analyze or avoid future problems and questions. This analysis of the past generates a future fear associated with a very real possibility: What are the chances of yellow fever spreading in densely populated regions of Asia? What are the chances of the emergence of a new pandemic caused by a virus that is already so well established on the planet? And in an associated way, the questions arise: All of these issues are relevant and worthy of analysis and response in future events, with a view to maximizing the health of the general population and mitigating human and economic damage.