The o'nyong nyong virus (ONNV), which stems from the Semliki Forest virus serocomplex, is an alphavirus closely related to the chikungunya virus (CHIKV), the Ross River virus (RRV), and the Mayaro virus (MAYV). ONNV is endemic in sub-Saharan Africa, transmitted by the bite of the Anopheles funestus and Anopheles gambiae mosquitos, and will typically cause sporadic and massive large-scale epidemics. Several cases have been reported in sub-Saharan Africa in the last 70 years, including outbreaks in Uganda and the Ivory Coast. It is likely that the virus has spread to a greater territory, but limited access to diagnostic tools as well as misdiagnosis as CHIKV may have contributed to a downplay of the estimation of the ONNV's spread. More than 2 million ONNV cases have been recorded; the incidence of infection currently seems to follow a downward trend.
Anopheline mosquito vectors (A funestus and A gambiae) are usually found around large bodies of water. The possibility of Aedes spp being additional vectors for ONNV has also been suggested. Transmission can follow endemic and enzootic cycles. Furthermore, familial clustering seems to play a great role in transmission.
ONNV infection is characterized by a nonhemorrhagic dengue-like clinical syndrome. Most patients who seek medical care present with fever, myalgia, noneffusive polyarthropathy with polyarthritis-polyarthralgia primarily in the large joints, headaches, posterior cervical lymphadenopathy-lymphadenitis, and a generalized, usually pruritic, maculopapular rash. Hemorrhagic manifestations are rare and include epistaxis and gingivorrhagia. Conjunctivitis is also a rare feature of ONNV infection. The case definitions associated with the highest specificity and sensitivity with laboratory-confirmed results combine symptoms of fever, lymphadenopathy, and polyarthralgia.
The incubation period is estimated to last 8 days, following which patients are incapacitated for a median time of 4 days. There are no reports of fatality due to ONNV; however, cases of spontaneous abortion have been associated with infection. ONNV disease is self-limited, but infection is responsible for morbidity and incapacity to work for several days, principally due to polyarthropathy. In some cases, polyarthropathy persists, with long-lasting, debilitating polyarthralgia.
Some studies estimate the ratio of apparent infection to asymptomatic infection is 2:1, but others argue that this is likely an underestimation.
No sex or age group seems to be more affected than another.
O'nyong nyong virus infection
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Synopsis
Codes
ICD10CM:
A92.1 – O'nyong-nyong fever
SNOMEDCT:
85579005 – O'nyong-nyong fever
A92.1 – O'nyong-nyong fever
SNOMEDCT:
85579005 – O'nyong-nyong fever
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Differential Diagnosis & Pitfalls
- CHIKV infection – Effusions are present in most cases of CHIKV-produced alphaviral polyarthropathy. Further, cervical lymphadenopathy is a distinct feature of ONNV infection and is rarely present in CHIKV-associated disease.
- Dengue virus infection – While ONNV infection often produces a nonhemorrhagic, dengue-like clinical syndrome, polyarthralgia is less common in dengue fever than in diseases caused by arthritogenic alphaviruses. Additional signs of vascular hyperpermeability, bicytopenia (thrombocytopenia with leukopenia), hepatocytolysis, and circulatory shock should point to dengue hemorrhagic fever. Clinical diagnosis is further confirmed with serology.
- MAYV infection – MAYV infection may present with retro-orbital pain, photophobia, dizziness, nausea, vomiting, and diarrhea. Myocarditis and neurological complications have also been reported.
- Measles – Prodromal features include coryza, cough, and conjunctivitis; prodromal features accelerate until the exanthem peaks. Koplik spots (minute, white or bluish-grayish papules on an erythematous base) may also develop in the palatal and jugal mucosa a few days prior to the exanthem.
- Malaria – Cyclic patterns of fever (tertian or quartan fever) may be present in malaria. Symptoms are otherwise nonspecific; patients may present with cough, nausea, vomiting, diarrhea, and diaphoresis in addition to classical alphaviral disease symptoms. Cutaneous implication is rare. Diagnosis is confirmed by characterization of parasitemia using light microscopy on Giemsa-stained peripheral blood smears.
- Zika virus infection – Symptomatic Zika virus infection manifests more often with conjunctivitis and peripheral arthralgia of the small joints. Diagnosis is by reverse transcription polymerase chain reaction (RT-PCR) and immunoglobulin M (IgM) serology if nucleic acid amplification is negative.
- RRV infection – RRV alphaviral disease produces polyarthralgia-polyarthritis associated with small effusions. Diagnosis is serological.
- Parvovirus B19
- Hepatitis viruses (see hepatitis A, B, C)
- Rubella virus
- Enteroviruses
- Adenoviruses
- Epstein-Barr virus
- Polyarticular septic arthritis – Polyarticular involvement in septic arthritis happens more often in patients with underlying connective tissue disease such as rheumatoid arthritis or systemic lupus erythematosus. Definitive diagnosis is provided by arthrocentesis and synovial fluid analysis.
- Other inflammatory polyarthropathies such as postinfectious arthritis
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Last Reviewed:08/31/2022
Last Updated:09/07/2022
Last Updated:09/07/2022