Circulation and Seasonality of Respiratory Viruses in Hospitalized Patients during Five Consecutive Years (2019-2023) in Perugia, Italy

Abstract

The emergence of SARS-CoV-2 and the non-pharmacological interventions adopted to counter its spread appear to have led to changes in the normal circulation and seasonality of respiratory viruses. Our study aims to investigate changes related to the circulation of respiratory viruses, not SARS-CoV-2, among hospitalized patients in Perugia, Central Italy, between 2019 and 2023. The samples were collected from individuals who went to the emergency room (ER) or were hospitalized and analyzed using a molecular multiplex test. The results underline that non-pharmaceutical interventions altered the typical seasonal circulation patterns of different respiratory viruses. Those mostly affected were enveloped viruses like influenza viruses that disappeared in 2021; the least impact was recorded for Rhinovirus, which was detected during the pandemic period, maintaining the same seasonality observed in the pre-pandemic period although with a reduction in the number of positive samples. Our data underline the importance of the continuous monitoring of these viruses, especially to understand the timing with which prevention measures, not only non-pharmacological interventions but also the equipment of vaccine doses and monoclonal antibodies, should be adopted to reduce their circulation, particularly in the population at risk of developing severe forms of lower respiratory tract infection.

Keywords: circulation; respiratory viruses; seasonality; surveillance.

Figure 1

Positivity rates of each respiratory virus per year.

Figure 2

Annual positivity rate of each virus in different age groups: (A) 0–4 years; (B) 5–14 years; (C) 15–44 years; (D) 45–64 years; (E) ≥65 years.

Figure 3

Monthly distribution of positive samples during the study period. (A) FLU; (B) RSV; (C) RHV.

Figure 4

Number of positive cases detected each month of the study period for human Coronavirus (hCoV), human Metapneumovirus (hMPV), Parainfluenza virus (PIV), Adenovirus (AdV), Bocavirus (BoV), and Enterovirus (ENV).