Characterizing the transmission patterns of seasonal influenza in Italy: lessons from the last decade [article]

Filippo Trentini, Elena Pariani, Antonino Bella, Giulio Diurno, Lucia Crottogini, Caterina Rizzo, Stefano Merler, Marco Ajelli
2020 medRxiv   pre-print
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 2010-2011 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
more » ... etected by the surveillance system. Influenza infection attack rate varied between 18.0% and 35.6% 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 1.1-1.4 (8 out of 10 seasons) and never exceeding 1.55. 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.
doi:10.1101/2020.11.29.20240457 fatcat:zar34n5br5ay7hcl66txvo7ipi