Genomic descriptive study of human Parvovirus B19 circulation during 2024/2025 in the State of Rio de Janeiro, Brazil

Purpose: Human Parvovirus B19 (B19V) infection is associated with a broad spectrum of clinical manifestations, including erythema infectiosum, arthropathy, transient red cell aplasia, hepatitis, and adverse fetal outcomes. Due to nonspecific presentations and limited routine testing, B19V infection often remains undiagnosed. Despite recent reports of increased B19V activity worldwide, contemporary data on its presence in Brazil remain scarce. We investigated the circulation of underdiagnosed pathogens in patients with suspected infectious diseases, prioritizing severe and fatal cases. Methods: In this descriptive study, hybrid capture-based whole-genome sequencing was used for a broad-range viral detection and characterization. We analyzed 472 clinical specimens selected for diagnostic investigation between 2024 and 2025, according to surveillance criteria for respiratory and arboviral infections, referred to the Public Health Laboratory of the state of Rio de Janeiro, Brazil. Results: B19V was the second most frequently detected viral pathogens, being identified in 190/472 specimens. Of these, just one sample had been previously tested for this pathogen. Thirty-one cases had higher B19V genomic coverage and were therefore selected for further analysis. Notably, B19V was the only virus detected with substantial genomic coverage in nine individuals, including elderly patients, and meningitis cases with B19V-positive cerebrospinal fluid. Phylogenetic analysis showed that recovered genomes clustered within genotype 1A2. Conclusions: B19V was frequently detected in patients undergoing investigation for infectious diseases and its circulation may represent an important and underrecognized pathogen. These findings support the incorporation of B19V testing into diagnostic algorithms for unexplained infectious diseases, especially in patients presenting atypical symptoms.