Exploring the drop in flu cases during the 2020-2021 season: The Italian case study

To explore the 2020-2021 influenza season by describing the case of Italy.

FluNet was searched for Italian data on virological samples. French, German, and Spanish data were collected for comparison. InfluNet was used for Italian epidemiological data on influenza-like illness (ILI). Data were extracted for the period from the 42nd week of 2020 to the 16th week of 2021 and for the previous 5-year period. The Containment and Health Index were used to describe the containment measures.

Among 6818 samples, 0% were positive in Italy in the 2020-2021 season (28.8% in the previous 5-year period; the percentage change in the total number of tested specimens was -51.3%). In France, Germany, and Spain, the percentage change was -23%, -7%, and -61%, respectively. The Italian ILI incidence remained below the baseline levels (mean 0.0144/100,000 inhabitants; range 0.0085-0.0204). In the previous 5-year period, the mean incidence was 0.041/100,000 inhabitants. With the increase in containment measures, a deflection of ILI incidence was described (P = .015).

Despite the reduced number of collected specimens compared to previous seasons and a slight rise in influenza vaccination rates, containment measures represent the most likely factor that helped to reduce cases in the 2020-2021 influenza season in Italy.