The O'nyong'nyong virus or O'nyong-nyong virus was a virus first isolated by the Uganda Virus Research Institute in Entebbe, Uganda in 1959. It is a togavirus (family Togaviridae), genus Alphavirus and is closely related to Chikungunya and Igbo Ora viruses. The name comes from the Nilotic language of Uganda and Sudan and means “weakening of the joints.”
There have been two epidemics of O’nyong’nyong fever. The first occurred from 1959-1962 spreading from Uganda to Kenya, Tanzania, Zaire (Democratic Republic of the Congo), Malawi and Mozambique, and affecting over two million people. This was one of the largest arbovirus epidemics recorded. The first virus isolates were obtained during this outbreak from mosquitoes and human blood samples collected from Gulu in northern Uganda in 1959.
The second epidemic in 1996-1997 affected 400 people and was confined to Uganda. The 35-year hiatus between the two outbreaks and evidence of an outbreak in 1904-1906 in Uganda indicates a 30-50 year cycle for epidemics.
According to: Journal of General Virology (2000), 81, 471-479. "...in Asia, the virus appears to be maintained in an urban cycle with Aedes aegypti mosquito vectors, while CHIK virus transmission in Africa involves a sylvatic cycle, primarily with Ae. furcifer and Ae. africanus mosquitoes."