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. 2024 Mar 31;65(1):E11-E16.
doi: 10.15167/2421-4248/jpmh2024.65.1.3179. eCollection 2024 Mar.

SARS-CoV-2 and influenza virus coinfections in the Tuscan population during the 2021/2022 influenza season

Giovanna Milano  1 , Serena Marchi  2 , Ilaria Vicenti  3 , Camilla Biba  3 , Lia Fiaschi  3 , Claudia Maria Trombetta  2   4 , Giacomo Lazzeri  2   4 , Emanuele Montomoli  2   4   5 , Ilaria Manini  2   4
Affiliations

SARS-CoV-2 and influenza virus coinfections in the Tuscan population during the 2021/2022 influenza season

Giovanna Milano et al. J Prev Med Hyg. .

Abstract

Introduction: The 2021/2022 influenza season was not characterised by a well-defined incidence peak. As reported by the Italian National Institute of Health, a high value of incidence of influenza cases was recorded in week 13, but it was still lower than in other influenza seasons. This abnormal circulation was probably due to relaxation of the COVID-19 pandemic restriction measures, such as social distancing, smart-working, home leaning and the use of masks, which greatly reduced the circulation of respiratory-transmitted viruses, including human respiratory syncytial virus (HRSV). The symptoms of SARS-CoV-2 and influenza are quite similar, sharing the human-to-human transmission route via respiratory droplets.

Methods: The aim of this study was to estimate the rate of coinfection with influenza viruses and/or HRSV in SARS-CoV-2-positive subjects (N = 940) in a population of central Italy during the 2021/2022 season.

Results: A total of 54 cases of coinfection were detected during the study period, 51 cases (5.4%) of SARS-CoV-2 and influenza virus and three cases (0.3%) of SARS-CoV-2 and HRSV coinfection.

Conclusions: These results highlight the importance of continuous monitoring of the circulation of influenza virus and other respiratory viruses in the context of the COVID-19 pandemic.

Keywords: Coinfection; Population; Respiratory viruses.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Figures

Fig. 1.
Fig. 1.
Incidence of influenza-like illness in Italy by week during the 2021/2022 influenza season, according to the Italian National Institute of Health [8].
Fig. 2.
Fig. 2.
Cases of coinfection with SARS-CoV-2 and human respiratory syncytial (HRSV), influenza A (IAV) or B (IBV) viruses from November 2021 to May 2022. Dashed vertical line separates first (left) and second (right) wave of influenza.
Fig. 3.
Fig. 3.
Cases of coinfection with SARS-CoV-2 and human respiratory syncytial (HRSV), influenza A (IAV) or B (IBV) viruses by age group. Dashed vertical line indicates the median age of the study population (30 years).
Fig. 4.
Fig. 4.
Representative results of PCR. Green fluorescence for Influenza A positive samples, blue fluorescence for HRSV positive sample.
See this image and copyright information in PMC

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