Epidemiology of Parvovirus B19 Infection In an Italian Metropolitan Area, 2012-2024: COVID-19 Pre-Pandemic, Pandemic and Post-Pandemic Trends.

Parvovirus B19 (B19V) is the most relevant human pathogenic virus in the Parvoviridae family. In years 2023-2024, a high incidence of B19V infections has been reported from many countries; we reconstructed the circulation of B19V in an Italian metropolitan area during the past 12 years (2012-2024), to elucidate evolving epidemiological trends and the impact of the COVID-19 pandemic. To this aim, we included a consecutive time-series analysis of the B19V laboratory investigation carried out in the Microbiology Unit, S.Orsola University Hospital of Bologna, Italy. A total of 29020 serum samples, from July 2012 to June 2024, were tested for the presence of both B19V IgG/IgM antibodies and/or for the presence of B19V DNA. Results were treated in aggregate form, by elaboration of demographic and laboratory data. Data reveal how circulation patterns of B19V have been conditioned by the COVID-19 pandemic. From 2012 until 2019, alternating phases of lower (years 2012-2014, 2017-2018) or higher (years 2015-2016, 2019) circulation were present, respectively 1.8%-2.6% and 4.7%-4.9% of tested patients. From 2020 to 2023, the lowest incidence of B19V infection was reported, 1.0%-1.3%. An unprecedented increase was observed in the first 6 months of 2024, up to 20.1%, mainly in the 0-10 and 41-50 age groups. In 2024, 53 infections were diagnosed in 115 pregnant women (46.1%). Our data highlight the epidemiological trends in B19V and confirm both the block during the COVID-19 pandemic and ensuing upsurge in transmission in 2024. The inclusion of B19V in rationally planned screening and diagnostic protocols appears justified in terms of appropriate surveillance and clinical management.