Surveillance for Dengue Virus and Other Pathogens in Patients with Acute Undifferentiated Febrile Illnesses in Yucatan, Mexico, During the Final Phase of the Coronavirus Disease 2019 Pandemic.

Acute undifferentiated febrile illness (AUFI) is associated with several etiological agents, including vector-borne pathogens. In tropical areas endemic for multiple pathogens, it is difficult to efficiently determine the etiology of AUFI. The goal for this study was to diagnose several arboviruses and other pathogens in patients with AUFI in Yucatan, Mexico, during the final phase of the coronavirus disease 2019 pandemic. A total of 215 patients with AUFI were included, with 170 from the urban area of Merida City and 45 from the rural area of the Molas community. Between December 2022 and December 2023, subjects were enrolled at health facilities, one in the rural area and two in the urban area. Overall, 36.7% (79/215) of AUFI patients were confirmed to have dengue virus (DENV). A significant difference (P <0.05) was found in the prevalence of dengue in the urban area (84.8%) compared with that in the rural area (15.2%). When diagnosed patients were grouped by age, most cases occurred in young adults (17-29 years old). Acute infections caused by Leptospira interrogans (L. interrogans) serovars Bratislava and Australis, Rickettsia spp., and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were also identified in patients with AUFI. In Merida City, five cases of multiple infections were found with dengue, SARS-CoV-2, and L. interrogans serovars Bratislava and Australis. In conclusion, DENV was confirmed as the main causative agent of AUFI in the present study; however, the simultaneous circulation of other relevant endemic causal agents that cause febrile infections in the area is a key point to consider when making differential diagnoses.