Oropouche virus screening among acute febrile illness cases in Thailand: no evidence of circulation in arboviral-endemic regions

Oropouche virus (OROV) causes Oropouche fever, an acute febrile illness with clinical symptoms similar to other arboviral infections. Accurate laboratory confirmation is essential to differentiate OROV from other tropical diseases and avoid inappropriate treatment. While the biting midge is the primary vector, several species of mosquitoes such as Culex quinquefasciatus are considered urban vectors. To date, the presence of OROV in other arbovirus-endemic regions including Thailand remains unknown. Given the widespread distribution of Cx. quinquefasciatus in Thailand and increasing incidence of OROV in the Americas, investigating the circulation of OROV within the country is crucial. This study aimed to monitor the prevalence of OROV among patients with acute febrile illness who were clinically suspected of arbovirus infection in Thailand. We re-analyzed 1374 sera samples collected between 2018 and 2023 from acute febrile illness patients who had previously tested negative for arboviruses known to endemic in Thailand. Quantitative RT-PCR of these samples revealed no amplification signal of OROV RNA, indicating no evidence of OROV infection in this retrospective cohort study. Continuous comprehensive surveillance across diverse regions nationwide, coupled with investigations of potential vectors within the country, is necessary for monitoring any future introduction of OROV into Thailand.