Physical distancing reduced the incidence of influenza and supports a favorable impact on SARS-CoV-2 spread in Mexico

Introduction: Physical distancing preventive measures were implemented in Mexico as a response to the coronavirus disease 2019 (CoViD-19) pandemic. School closures occurred on March 16, 2020, in 10 out of 32 Mexican states, and one week later in the remaining states. Because the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the influenza virus have similar transmission mechanisms, we aimed to evaluate the impact of physical distancing on the incidence of influenza as a proxy of the impact on SARS-CoV-2 contagion. Methodology: A national flu surveillance system was cross-sectionally analyzed and daily average percent changes (APCs) of incidence rates were calculated throught Poisson regression models. Results: Greater decreasing trends (APCs -8.8, 95% CI: -12.5, -4.5; vs. -6.0, 95% CI: -9.9, -2.0; p = 0.026) were documented in the states with earlier school closures and across age groups, suggesting that earlier implementation of physical distance results in reduced SARS-CoV-2 spread. Conclusions: Physical distancing policies decrease the incidence of influenza infections in Mexico; its favorable impact on the spread of SARS-CoV-2 is commendable.