A self-limiting viral disease characterized by arthralgia or arthritis, primarily in the wrist, knee, ankle and small joints of the extremities, lasting days to months. In many patients, onset of arthritis is followed after 1–10 days by a maculopapular rash, usually non-pruritic, affecting mainly the trunk and limbs. Buccal and palatal enanthema may occur. The rash resolves within 7–10 days, and is followed by a fine desquamation. Myalgia, fatigue, fever and lymphadenopathy are common. Paresthesias and tenderness of palms and soles occur in a small percentage of cases. Persistence of joint pains, arthritis, myalgia and/or fatigue occurs in 10–50% of cases.
Chikungunya causes a more severe illness, with high fever, prominent lymphadenopathy and leukopenia, and a prolonged convalescence. Mild hemorrhagic disease can occur with Mayaro virus disease and with chikungunyavirus disease (see Dengue hemorrhagic fever). Rare deaths and occasional severe congenital infections occur due to chikungunya virus infection.
Serological tests show IgM in acute serum samples, and a rise in titers to alphaviruses between acute and convalescent samples. IgM commonly persists for weeks or months.
Ross River, Barmah Forest viruses, Sindbis (in Africa and Europe), Mayaro, chikungunya and o'nyong-nyong viruses cause similar illnesses. Ockelbo, Pogosta and Karelian fever are due to Sindbis virus.
Diagnosis may be made by RT-PCR on blood, particularly for chikungunya. Virus may be isolated from blood in the first few days of illness, using newborn mice, mosquito inoculation, or cell culture.
Mode of Transmission
Ross River virus and Barmah Forest virus are transmitted by Culex annulirostris, Ae. vigilax, and other Aedes spp.; chikungunya virus by Ae. aegypti and Ae. albopictus in Asia, other Ae. Spp in Africa and Australia; o'nyong-nyong virus by Anopheles spp.; Sindbis virus by various Culex spp., Ae. spp. and Culex spp.; Mayaro virus by Haemagogus spp.
From 3 to 12 days, usually 7 to 9 days.
Period of Communicability
No evidence of direct person-to-person transmission. Humans are infectious to mosquitoes for the first few days after onset of illness. Infected individuals can introduce virus into receptive areas, e.g. chikungunya virus and Ross River virus.
Marsupials, especially kangaroos and wallabies for Ross River virus and Barmah Forest virus; primates for chikungunya; birds for Sindbis; unknown for Mayaro virus and o'nyong-nyong virus. Trans-ovarial transmission of Ross River virus has been demonstrated in Aedes vigilax.
Recovery is universal, though some take several months, and followed by lasting homologous immunity; second attacks are unknown. Unapparent infections are common, especially in children, among whom the overt disease is rare.
Outbreaks of disease occur during warm and wet conditions that favor proliferation of the mosquito vectors. Ross River virus disease occurs annually in Australia, occurring in December to March in temperate regions, and in the wet season from December to June in tropical areas. Infections may also occur in normally arid regions following irregular heavy rain with flooding. Sporadic cases occur in the colder regions of southern Australia and in Papua New Guinea. In 1979, an outbreak in Fiji spread to other Pacific islands, including American Samoa, the Cook Islands, and Tonga. Barmah Forest virus infection occurs in the same regions as Ross River virus infections, but is less common. Chikungunya virus occurs in Africa, southeastern Asia, India, Sri Lanka, and the Philippines, and has caused a major epidemic throughout the Indian Ocean region since 2004. Sindbis virus disease occurs in Africa and northern Europe, but is rare in Asia and Australia. Outbreaks occur in summer and autumn in Europe and South Africa. Pogosta disease in Finland has a seven-year cycle. O'nyong-nyong virus is known only from Africa; epidemics in 1959–1963 and 1996–1997 involved millions of cases throughout eastern Africa. Mayaro virus occurs in Central America, northern South America and Trinidad. Sporadic cases and occasional outbreaks occur in endemic areas.
Prevention and Control
1) Preventive measures:
General measures applicable to mosquito-borne viral encephalitides.
2) Control of patient, contacts and the immediate environment:
b) Isolation: To avoid further transmission, advise patients not to travel to areas with vector mosquito species for the first few days after onset of symptoms, and provide advice about mosquito protection.
c) Concurrent disinfection: Not applicable.
d) Quarantine: Not applicable.
e) Immunization of contacts: Not applicable.
f) Investigation of contacts and source of infection: Search for unreported or undiagnosed cases wherever the patient lived during the 2 weeks prior to onset; check all family members serologically.
g) Specific treatment: None.
3) Epidemic measures:
Same as for arthropod-borne viral fevers.
4) Disaster implications:
5) International measures:
WHO Collaborating Centres provide support as required.
Source: Heymann (Ed.). (2008). Control of Communicable Diseases Manual, 19th edition. Washington, DC: American Public Health Association.