O'nyong'nyong virus (ONNV) was first isolated by researchers at the Uganda Virus Research Institute in Entebbe,

Uganda Uganda, officially the Republic of Uganda, is a landlocked country in East Africa. It is bordered to the east by Kenya, to the north by South Sudan, to the west by the Democratic Republic of the Congo, to the south-west by Rwanda, and to the ...

, during a large outbreak of a disease in 1959 that resembled

dengue fever Dengue fever is a mosquito-borne disease caused by dengue virus, prevalent in tropical and subtropical areas. Asymptomatic infections are uncommon, mild cases happen frequently; if symptoms appear, they typically begin 3 to 14 days after i ...

. 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 name was given to the disease by the Acholi tribe during the 1959 outbreak. The name comes from the Nilotic language of Uganda and

Sudan Sudan, officially the Republic of the Sudan, is a country in Northeast Africa. It borders the Central African Republic to the southwest, Chad to the west, Libya to the northwest, Egypt to the north, the Red Sea to the east, Eritrea and Ethiopi ...

and means "weakening of the joints". The virus can infect humans and may cause disease.

Signs and symptoms

Common symptoms of infection with the virus are polyarthritis,

rash A rash is a change of the skin that affects its color, appearance, or texture. A rash may be localized in one part of the body, or affect all the skin. Rashes may cause the skin to change color, itch, become warm, bumpy, chapped, dry, cracke ...

and

fever Fever or pyrexia in humans is a symptom of an anti-infection defense mechanism that appears with Human body temperature, body temperature exceeding the normal range caused by an increase in the body's temperature Human body temperature#Fever, s ...

. Other symptoms include eye pain, chest pain,

lymphadenitis Lymphadenopathy or adenopathy is a disease of the lymph nodes, in which they are abnormal in size or consistency. Lymphadenopathy of an inflammatory type (the most common type) is lymphadenitis, producing swollen or enlarged lymph nodes. In cl ...

and lethargy. The disease is self-limiting. No fatalities due to infection are known.

Cause

Strains

ONNV has at least three major subtypes, or strains, the genomic sequences of which are currently available on genome databases.

Transmission

ONNV is transmitted by bites from an infected

mosquito Mosquitoes, the Culicidae, are a Family (biology), family of small Diptera, flies consisting of 3,600 species. The word ''mosquito'' (formed by ''Musca (fly), mosca'' and diminutive ''-ito'') is Spanish and Portuguese for ''little fly''. Mos ...

. It is the only virus whose primary vectors are anopheline mosquitoes ('' Anopheles funestus'' and '' Anopheles gambiae'').

Epidemiology

There have been two epidemics of o'nyong'nyong fever. The first occurred from 1959 to 1962, spreading from Uganda to

Kenya Kenya, officially the Republic of Kenya, is a country located in East Africa. With an estimated population of more than 52.4 million as of mid-2024, Kenya is the 27th-most-populous country in the world and the 7th most populous in Africa. ...

Tanzania Tanzania, officially the United Republic of Tanzania, is a country in East Africa within the African Great Lakes region. It is bordered by Uganda to the northwest; Kenya to the northeast; the Indian Ocean to the east; Mozambique and Malawi to t ...

, Zaire (

Democratic Republic of the Congo The Democratic Republic of the Congo (DRC), also known as the DR Congo, Congo-Kinshasa, or simply the Congo (the last ambiguously also referring to the neighbouring Republic of the Congo), is a country in Central Africa. By land area, it is t ...

Malawi Malawi, officially the Republic of Malawi, is a landlocked country in Southeastern Africa. It is bordered by Zambia to the west, Tanzania to the north and northeast, and Mozambique to the east, south, and southwest. Malawi spans over and ...

and

Mozambique Mozambique, officially the Republic of Mozambique, is a country located in Southeast Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west, and Eswatini and South Afr ...

, and affecting over two million people, one of the largest

arbovirus Arbovirus is an informal name for any virus that is Transmission (medicine), transmitted by arthropod Vector (epidemiology), vectors. The term ''arbovirus'' is a portmanteau word (''ar''thropod-''bo''rne ''virus''). ''Tibovirus'' (''ti''ck-''bo ...

epidemics ever 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 was confined to Uganda. The 35-year hiatus between the two outbreaks and evidence of an outbreak in 1904–1906 in Uganda indicate a 30–50 year cycle for epidemics. 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. In 2015–2016 there was a minor outbreak in Uganda with 51 suspected cases. There has been a minor outbreak in Mombasa (Kenya) and the County Government of Mombasa issued a warning. A 2015 study indicated that ONNV is endemic in coastal East Africa, along with chikungunya virus.

References

External links

{{Taxonbar, from=Q1407583 Alphaviruses Arthropod-borne viral fevers and viral haemorrhagic fevers