Speaker
Description
The introduction of the hepatitis A virus (HAV) vaccine in nine Latin American countries has impacted HAV epidemiology, requiring continuous monitoring of viral strains. This study aimed to molecularly characterize and evolutionarily analyze Argentine HAV-IA strains.
From 2016 to 2023, 78 and 109 RNA-HAV+ clinical and wastewater samples, respectively, were analyzed by RT-Nested PCR targeting VP1/2A genomic region (900bp), from which 32 could be amplified and sequenced. A 150-sequence dataset was built, including all Latin American sequences available on GenBank until 31-5-2023; 32 sequences obtained in this study; and the first 10 sequences with the highest score in BLAST analysis. IQ-Tree v.2, BEAST 1.8.2, and SpreadD3.jar were conducted for phylogeny, coalescence, and phylogeography, respectively.
Phylogenetic analysis revealed a main HAV cluster with sequences from European and Latin American outbreaks in men who have sex with men (MSM) and Argentine isolates obtained in this study from: a-a local MSM outbreak in 2017-2019; b-2022-2023 clinical cases; and c-wastewaters from the same years. Within this clade, Argentine strains clustered into three groups by periods (2017-2018; 2018-2019; 2022-2023). The other sequences obtained grouped intermingled with worldwide variants and previous endemic Argentine strains from different sources and years.
Coalescence analysis showed that the most recent common ancestor would have existed around 1942 [95%HPD:1929-1954] in Uruguay. The estimated substitution rate was 4.85×10ˉ4 [95%HPD:3.4×10ˉ4–6.4×10ˉ4] substitutions/site/year, comparable to previously described rates.
The phylogeographic approach suggests multiple HAV introductions into Argentina from diverse regions, contributing to the occurrence of local outbreaks. Wastewater surveillance mirrored the clinical-epidemiological scenario of viral circulation, reflecting HAV majority variants circulating in the population during different periods. Other low-frequency strains were found only in clinical samples, causing symptomatic infections, mainly affecting susceptible young adults.
This study highlights phylodynamic approaches to monitor HAV circulation dynamics, trace the origin of outbreaks, and support public health measures.
