Genotypic Characterization of Human Parvovirus B19 Circulating in the 2024 Outbreak in Tuscany, Italy

Abstract

Human Parvovirus B19 (hB19V) is a widespread virus, causing erythema infectiosum in children and several clinical manifestations from acute to persistent infections in adults. In early 2024, ECDC reported an increased human Parvovirus B19 circulation in 14 European countries. A hB19V outbreak was also reported in Tuscany, Italy, prompting a detailed investigation of its genetic characteristics. In this context, through strict monitoring of circulating strains via next-generation sequencing (NGS), we carried out a phylogenetic analysis based on the whole of hB19V genomes. Phylogenetic clustering assigned all isolates to the G1a genotype, although with some mutations in NS1, VP1, and VP2, compared to the reference strains. Further characterization of these variants is necessary to fully assess their potential implications for public health. This study provides valuable insights into the spread of Parvovirus B19 and underlines the importance of continuous genomic surveillance to monitor and respond to possible hB19V epidemics that could impact public health.

Keywords: G1a genotype; Parvovirus B19; outbreak.

Figure 1

A representation of the hB19V genome. The 5596nt genome is composed of 5′ and 3′ inverted terminal repeats, and three main genes: the non-structural protein1 (NS1), the viral protein 1 (VP1), and the viral protein 2 (VP2). The two proteins share the whole sequence of VP2, but VP1 has an additional N-terminal domain known as the VP1 unique region (VP1u).

Figure 2

Parvovirus B19 cases from 2023 to the end of September 2024 in Siena area, Italy. (A) Number of positive samples distributed by gender; blue bars are from males and purple bars from females. (B) Number of positive samples distributed by age; green bars represent adult patients (>15 years old), and yellow bars correspond to children. This study showed that the hB19V infection was more frequent in adult females.

Figure 3

Phylogenetic tree of NGS samples. The phylogenetic tree shows that all samples were clustered under the genotype 1a. No samples were clustered under the genotype 1b, genotype 2, and genotype 3. The used references are highlighted in bold, all of them are accessible in the Genbank database. Genotype 1A: NC_00083.2; AF162273.1; genotype 1B:DQ357065.1; genotype 2: AY044266.2; AY064475.1; and genotype 3: AY083234.1; AX003421.1.