The aim is to analyse that, during the current pandemic situation, the reduction in the number of cases of influenza suggests that the non-pharmaceutical interventions (NPIs) applied to contain the expansion of SARS-CoV-2 also affect the influenza expansion. We analyse the interaction of influenza and SARS-CoV-2 spread based on an extended SEIRD model for the Catalonia region in Spain. We show that the dynamic evolution of the spread of SARS-CoV-2 and influenza generates a small interference. This interference causes a small reduction in the number of cases of seasonal influenza, reducing its expansion over the population. Other elements like the face mask mandates, social distancing and hand cleaning boost the reduction in both expansions. Influenza expansion will present a small reduction in the number of cases due to the interaction with SARS-CoV-2 expansion but mainly because the NPIs applied to the population.