Because immunological defense against pathogens is expensive and merely reactive, human antipathogen defense is also characterized by proactive behavioral mechanisms that inhibit contact with pathogens in the first place. This behavioral immune system comprises psychological processes that deduce the risk of contagion from environmental cues and that respond to these cues by activating aversive behaviors. These processes have important effects on human social cognition and social behavior, including implications for sexual behavior. This is particularly important when new infectious diseases (for example, COVID-19) are spreading through the population. In this perspective, the objective of this research is to understand, from an evolutionary perspective, the dynamics of the sexual behavior of singles and non-singles during the pandemic of COVID-19 and how this behavior is intertwined with the hypothesis of the behavioral immune system. For this, the research will be carried out through a set of online questionnaires, composed of a sociodemographic questionnaire, a questionnaire for investigating sexual behaviors, the Generalized Anxiety Disorder Scale, the Perceived Vulnerability Questionnaire to Disease, the Subscale of Disgust of pathogens, Evaluation as a romantic partner, and the reduced version of the inventory of sociosexuality.