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BMC Public Health
. 2022 Jan 6;22(1):19.
doi: 10.1186/s12889-021-12426-9.
Characterizing the transmission patterns of seasonal influenza in Italy: lessons from the last decade
Filippo Trentini 1 2 , Elena Pariani 3 , Antonino Bella 4 , Giulio Diurno 5 , Lucia Crottogini 6 , Caterina Rizzo # 7 , Stefano Merler # 8 , Marco Ajelli # 9
Affiliations
- PMID: 34991544
- DOI: 10.1186/s12889-021-12426-9
Abstract
Background: Despite thousands of influenza cases annually recorded by surveillance systems around the globe, estimating the transmission patterns of seasonal influenza is challenging.
Methods: We develop an age-structured mathematical model to influenza transmission to analyze ten consecutive seasons (from 2010 to 2011 to 2019-2020) of influenza epidemiological and virological data reported to the Italian surveillance system.
Results: We estimate that 18.4-29.3% of influenza infections are detected by the surveillance system. Influenza infection attack rate varied between 12.7 and 30.5% and is generally larger for seasons characterized by the circulation of A/H3N2 and/or B types/subtypes. Individuals aged 14 years or less are the most affected age-segment of the population, with A viruses especially affecting children aged 0-4 years. For all influenza types/subtypes, the mean effective reproduction number is estimated to be generally in the range 1.09-1.33 (9 out of 10 seasons) and never exceeding 1.41. The age-specific susceptibility to infection appears to be a type/subtype-specific feature.
Conclusions: The results presented in this study provide insights on type/subtype-specific transmission patterns of seasonal influenza that could be instrumental to fine-tune immunization strategies and non-pharmaceutical interventions aimed at limiting seasonal influenza spread and burden.
Keywords: Burden; Eproduction number; Seasonal influenza; Susceptibility to infection.