The virological surveillance of influenza in Castile and Leon (Spain) during the 2019-2020 influenza season was characterized by the mixed circulation of both A(H1N1)pdm09 & influenza B viruses, being predominantly the A(H1) Only a few percentages of A(H3N2) subtype was detected during this period.

The first case of influenza infection was identified in week 43/2020, and corresponded to one hospitalized child (female; 4 years old) infected by Influenza B type The first case in the Sentinel Network was identified in week 48/2019 in a child (male; 11 years old) infected also by an influenza B type virus.