Integrated Clinical and Environmental Surveillance Provides the First Evidence of Aichi Virus Circulation in Córdoba, Argentina.

Human Aichi virus (AiV-A1), a member of the Kobuvirus genus associated with viral gastroenteritis, remains largely underdiagnosed in Latin America due to the absence of routine testing and limited epidemiological data. This study provides the first molecular evidence of AiV-A1 circulation in Argentina to date, based on the analysis of wastewater and pediatric stool samples collected in Córdoba between 2012 and 2019. A total of 93 untreated wastewater samples from the main wastewater treatment plant and 155 stool samples from children with acute gastroenteritis (AGE) were screened using a validated nested RT-PCR targeting the 3CD region, followed by sequencing and phylogenetic analysis. AiV-A1 was detected in 58% of wastewater samples, demonstrating continuous, year-round circulation without a defined seasonal pattern. Among clinical AGE cases, AiV-A1 was identified in 21.5%, including 10.3% as monoinfections. Inclusion of AiV-A1 in the diagnostic panel within this study, increased the overall viral detection rate from 62% to 69%, suggesting that its incorporation into routine diagnostics could improve the detection of virologically confirmed diarrhea cases. Phylogenetic reconstruction showed that all Argentine strains clustered within genotype B, forming two intragenotypic lineages and exhibiting high nucleotide identity (94.8%-99.6%) between environmental and clinical isolates. Together, these findings provide the first evidence of endemic AiV-A1 circulation in Argentina, highlight its potencial role in pediatric gastroenteritis, and establish a baseline for future regional epidemiological studies while offering relevant insight into the burden, transmission, and molecular epidemiology of AiV-A1 in the country.