Bert F, Cugudda E, Moro GL, Galvagno PF, Siliquini. Exploring the drop in flu cases during the 2020-2021 season: the Italian case study. Ann Epidemiol. 2022 Oct 20:S1047-2797(22)00246-0
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 five-year period. The Containment and Health Index was used to describe the containment measures.
Results: Among 6818 samples, 0% were positive in Italy in the 2020-21 season (28.8% in the previous five-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 baseline levels (mean 0.0144/100,000 inhabitants; range 0.0085-0.0204). In the previous five-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=0.015).
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.
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