Objective This study aimed to evaluate the performance, before and during the COVID-19 pandemic, of the case definition of suspected influenza used in community surveillance in Mexico . Methods A cross-sectional analysis of a cohort study took place and cases fulfilling the suspected case criteria (n = 20,511), and with laboratory-conclusive evidence (quantitative real-time polymerase chain reaction) to confirm or discard influenza virus infection, were analyzed . Results A high sensitivity and modest specificity were documented, and this later decreased during the COVID-19 outbreak, as well as its diagnostic accuracy . However, no significant differences were observed in the area under the receiver operating characteristics among the analyzed periods . Conclusions The evaluated case definition remains to be a cost-effective alternative to identify patients who may benefit from influenza-specific antiviral drugs, even during the COVID-19 global outbreak.