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

Abstract

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

Methods: 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.

Results: 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).

Conclusions: 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.

Keywords: Covid-19; Ili; Influenza.