AimsTo investigate the molecular epidemiology, especially temporal variations in genotype distribution, of sapoviruses and Aichi virus 1 (AiV-1) in Arizona, United States, by examining wastewater. Methods and ResultsA total of 26 wastewater samples (13 influent and 13 effluent) were collected monthly from a wastewater treatment plant and viral strains were identified through nested reverse transcription-PCR followed by cloning and sequencing analysis. Identified sapovirus strains were classified into seven genotypes belonging to three genogroups (GI, GII, and GV): GI.1, GI.2, GI.3, GII.1, GII.2, GII.8 and GV.1, with a clear temporal shift. The majority of AiV-1 strains identified from the wastewater samples were classified into genotype B, and genotype A strains were identified in only two samples. ConclusionsWe identified a number of sapovirus and AiV-1 strains belonging to multiple genotypes in wastewater samples collected over a 13-month period. Our results suggested a temporal shift in prevalent genotypes in the community. Significance and Impact of the StudyThis is the first study elucidating the genotype distribution of human sapoviruses and AiV-1 in wastewater in the United States. Wastewater surveillance is especially useful for understanding molecular epidemiology of viruses that are less commonly tested in clinical diagnosis, including sapoviruses and AiV-1.