Information Sheet - Chikungunya Fever

Infectious Agent

Arthropod-borne alphavirus from Togaviridae family.

Geographic Distribution

Africa, India, Southeast Asia and the Philippines. Outbreak in Italy (2007)

Mode of Transmission

Transmitted by Aedes sp. mosquitos (A. egytpi. A. albopictus). No evidence of human to human transmission. Intra-uterine transmission has been documented.

Incubation Period

1-12 days

Clinical Presentation

Patients present with fever, fatigue, headache, myalgia and severe arthralgia/arthritis typically involving peripheral joints such as the wrists, ankles, proximal inter-phalangeal joints (PIP) and distal inter-phalangeal joints (DIP). The involved joints are painful, swollen and have reduced range of motion. Proximal joints such as the shoulders, hips and knees can also be involved. Patients frequently develop a macular or maculopapular rash which can be accompanied by generalized pruritis and conjunctivitis. Flu-like symptoms generally last for 3-7 days while joint symptoms usually last for several weeks to several months.

Laboratory tests are usually within normal limits however leucopenia, thrombocytopenia and elevated liver enzymes (ALT, AST) have all been observed during the first few weeks of infection. Radiological investigations are also normal.

Although it is generally considered a self-limiting disease, deaths have occurred in patients in the developing world. Severe complications such as meningoencephalitis and thrombocytopenia-associated hemorrhage have also been documented. Newborn, elderly and immuno-compromised patients as well as patients with chronic medical conditions appear to be at increased risk for such complications.

Chikungunya is most easily confused with Dengue, which has a similar presentation and is transmitted by the same vector across the same geographic distribution. However, debilitating and persistent joint involvement is more characteristic of Chikungunya infection. Other alphaviruses found in Africa and Asia such as Sindbis and O’nyong nyong also cause fever and polyarthritis. Canadians have become infected with Chikungunya after travel to areas where it is endemic.

Diagnosis

Chikungunya can be diagnosed using virus isolation, RT-PCR or serological techniques. Virus isolation is the most definitive test but it can only be used during the first week of infection and results typically take 1-2 weeks. RT-PCR can be used at any time and results are typically available in 1-2 days. Serological diagnosis can be made by identifying Chikungunya-specific IgM antibodies in acute serum or a 4-fold rise in IgG antibody titres between acute and convalescent sera. ELISA techniques are generally used but may need to be confirmed with HIA as there is cross-reactivity between alphaviruses. Public health authorities should be alerted if diagnostic tests are positive.

Treatment

Supportive treatment only, including fluids, acetaminophen and non-steroidal anti-inflammatory medications for joint pain. ASA is generally avoided because of the risk of hemorrhage.

Prevention

Patients should be advised to take precautions to avoid mosquito bites if travelling in an area where Chikungunya is known to occur. Such measures include use of DEET-based insect repellent to exposed skin, wearing light-coloured clothing with full-length pant legs and sleeves and trying whenever possible to remain in well-screened or completely enclosed, air-conditioned areas during peak biting times. Once infected, patients should continue to avoid mosquito bites to prevent further dissemination of the virus. Infection is thought to confer life-long immunity.

References

Pialoux G, Gouzere BA, Jaurguiberry S, Strobel M. Chikungunya, an Epidemic Arbovirus. Lancet Infect Dis 2007: 319-27.

Taubitz W et al. Chikungunya Fever in Travellers: Clinical Presentation and Course. CID 2007:45 e1-e4.

Other Information Sheets

CDC webpages on Chikungunya. CDC March 2008. Available at: http://www.cdc.gov/ncidod/dvbid/Chikungunya/

WHO Information Sheet on Chikungunya. WHO May 2008. Available at: http://www.searo.who.int/en/Section10/Section2246.htm

ECDC Fact Sheet on Chikungunya. ECDC May 2008. Available at: http://ecdc.europa.eu/Health_topics/Chikungunya_Fever/Disease_facts.htm