[Yezo virus and emerging orthonairovirus diseases].

A new etiological agent of an acute febrile illness following tick bite has been found in Hokkaido, Japan, in 2019 and designated as Yezo virus. Seven cases of Yezo virus infection were identified from 2014 to 2020 by passive and retrospective surveillance. Yezo virus is classified into the genus Orthonairovirus, family Nairoviridae and forms Sulina genogroup together with Sulina virus, which was identified in ticks in Romania. The Sulina genogroup viruses are closely related to the Tamdy genogroup viruses recently reported as causative agents of febrile illness in China and distant from known orthonairovirus pathogens, such as Crimean-Congo hemorrhagic fever virus. Since only limited information is available for the emerging orthonairovirus diseases, including Yezo virus infection, their occurrence should be carefully monitored.