HEV-3 subtypes and strains detected in cases of HEV infection in central Italy from 2015 to 2023

Fig. 1. Monthly distribution of cases observed in the period 2015–2023, in which cases from a HEV outbreak occurred in Central Italy in 2019 are highlighted (orange end of the bars)

Fig. 2. Phylogenetic trees for HEV subtyping, obtained by the Maximum Likelihood approach. (A) Analysis of n = 52 sequences, size 493 nt. (B) Analysis of n = 66 sequences, size 411 nt. Both trees include 39 Reference sequences representing subtypes 3a to 3 m, as reported in Smith et al., 2020 [2]. The meaning of the red and black dots is reported in the insert in the lower right corner of the figure

Fig. 3. (A) Subtype distribution, HEV infection cases (n = 118) from Abruzzo and Lazio, 2015–2023. (B) Annual trend of subtype distribution of 3f, 3e and 3c cases from Abruzzo and Lazio, 2015–2023. The annual number of cases in the years 2015, 2020, 2021, 2022 was not large enough (n = 3, n = 7, n = 7 and n = 3, respectively) to give rise to a reliable annual distribution. Thus, cases from 2015 were joined to 2016, cases from 2020 were joined to 2021 and cases from 2022 were joined to 2023. (C) Monthly distribution of 3f, 3e and 3c subtype cases cumulatively observed in the period 2015–2023 in Abruzzo and Lazio, including 3f and 3e cases from the 2019 outbreak. (D) Monthly distribution of 3f, 3e and 3c subtype cases after exclusion of the 3f and 3e cases from the 2019 outbreak

Fig. 4. Phylogenetic tree resulting from analysis of a 370 nt region shared by the HEV sequences obtained with different protocols (n = 118). A Maximum Likelihood approach was applied, with a GTR + G + I evolutionary model preliminarily estimated by the Model tool in MEGA. The tree includes reference sequences (n = 39) representing subtypes 3a to 3 m, as reported in in Smith et al., 2020 [2]. The meaning of red, blue and black circles is described in the box. Clusters are delimited by red lines and marked by alphabetical letters, A to N