[1] ONNV is a togavirus (family Togaviridae), genus Alphavirus, is closely related to the chikungunya and Igbo Ora viruses, and is a member of the Semliki Forest antigenic complex.
The first occurred from 1959 to 1962, spreading from Uganda to Kenya, Tanzania, Zaire (Democratic Republic of the Congo), Malawi and Mozambique, and affecting over two million people, one of the largest arbovirus epidemics ever recorded.
[6][7] The first virus isolates were obtained during this outbreak from mosquitoes and human blood samples collected from Gulu in northern Uganda in 1959.
[10] In 2013, ONNV was confirmed as the cause of disease in a 60-year-old German woman who became infected while traveling in East Africa.
[12] A 2015 study indicated that ONNV is endemic in coastal East Africa, along with chikungunya virus.