In South America, an increase in the number of reports on Hepatitis E Virus (HEV) circulation has been registered in recent years, showing a wide viral circulation on the continent (Pisano et al., 2020). Despite this evidence of HEV circulation, it is believed to be an underestimated and poorly understood virus in our country, and, consequently, it is not routinely tested (Pisano et al., 2020).
Since HEV is transmitted mainly by the fecal-oral route, the virus is shed in the stools of infected persons (symptomatic and asymptomatic as well) and discharged into the wastewaters (World Health Organization (WHO) 2023). Wastewater-based epidemiology (WBE) has been used for monitoring infectious diseases since the 1940s, and in the past 20 years, WBE has taken a greater relevance for a wide variety of other enteric viruses, and its application as an early warning system and variant tracking method in parallel with clinical epidemiological surveillance (Gao et al., 2023; Verani et al., 2024). Globally, it has been extensively demonstrated the occurrence of HEV in water environments, particularly in untreated waters (Takuissu et al., 2022).
A recent study led by Dr. Anabella Clara Fantilli and Dr. Viviana Elizabeth Ré aimed to monitor the circulation of HEV from wastewater samples collected during a six-year period and compare these results with clinical surveillance in the central region of Argentina. From 2017 to 2022, 1008 raw wastewater samples were analyzed, including four wastewater treatment plants from four cities (n=319), and 7 local neighborhood collector sewers in Córdoba city (n=689). Serum and/or stool samples from patients suspected of HEV infection were also analyzed (n=48). HEV molecular detection and viral load quantification were performed by real time RT-qPCR, and genetic characterization by two RT-Nested PCRs (targeting partial ORF-1 and ORF-2 genomic regions), Sanger sequencing and phylogenetic analysis (MEGA v11, IQ-TREE, FigTree softwares).
Fifty-three (5.3%) wastewater samples were RNA-HEV positive by real time RT-qPCR, with variations according to the location and year (0.0% – 21.6%). Out of these, ORF-2 genomic region was amplified in 20 samples (37.7%) and ORF-1 partial region in 12 (22.6%), and eighteen sequences were obtained. Throughout the study period, two (4.2%) HEV confirmed infections were reported, and one sequence was obtained. Phylogenetic analyses for both genomic regions showed that all the isolates were genotype HEV-3 clade abchijklm.
This study revealed the presence of HEV in wastewaters across central Argentina over a six-year period, despite a low number of clinical cases, suggesting a cryptical circulation of the virus, with the possible presence of abundant subclinical infections. Given that national surveillance of clinical HE cases may not fully represent all circulating genotypes within the population, our findings highlight WBE as an effective tool for public health services to identify viral diversity. This study emphasizes the importance of urban WBE as a complement to traditional clinical surveillance and a valuable strategy for public health surveillance systems, providing situational awareness of changes in the transmission, circulation, burden, and genetic diversity of HEV strains over time in the community.
Read the full article (Water Research. 2024 Jun 4:164:105000): DOI: https://doi.org/10.1016/j.watres.2024.122004
