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Chikungunya
virus (CHIKV) is a togavirus belonging to the genus alphavirus,
indigenous to tropical Africa and Asia, where it is transmitted to
humans by the bite of infected mosquitoes, usually of the genus Aedes.
Chikungunya (CHIK)
fever, the disease caused by CHIKV, was first recognized in epidemic
form in East Africa during 1952-1953.
Since the
beginning of 2006, this crippling mosquito-borne disease (Chikungunya
virus infection) has shown an explosive emergence in nations in the
Indian Ocean area. By March 7, 2006, 157,000 people had been infected
in the French island La Reunion, and the disease had spread to the
islands of Seychelles, Mauritius, and Mayotte (French). Subsequently,
the disease appeared in India, China, and European countries.
Infection in
Aedes aegypti salivary glands is asymptomatic and lifelong. It is
transmitted by Aedes aegypti to human, there is no human to human
transmission.
The disease is
highly infectious.
Its main
symptoms are sudden onset of chills, fever, headache , rash, and debilitating arthralgia .
The symptoms may persist for several weeks.
The word "chikungunya"
is thought to derive from description in local dialect of the
contorted posture of patients afflicted with the severe joint pain
associated with this disease.
May rarely
cause hemorrhagic fever, specially in children.
Incubation
period is 1 to 12 days. Fever lasts for 3 - 7 days, arthralgia may
persit for upto 3 weeks.
Because CHIK
fever epidemics are sustained by human-mosquito-human transmission,
the epidemic cycle is similar to those of dengue and urban yellow
fever.
Large
outbreaks of CHIK fever have been reported recently on several islands
in the Indian Ocean and in India.
Though fetal
contamination risks appear to be rare before 22 weeks of gestation,
they are potentially dangerous. After 22 weeks gestation, newborns
infection occurs if the mother is viremia positive at delivery.
Transplacental transmission is suspected, but the pathogenic mechanism
remains unknown.
Warm, humid
climates and water reservoirs serve as an excellent breeding ground
for the vector of the virus, Aedes mosquitoes. With an
increase in temperature, susceptibility of mosquitoes to CHIKV
increases.
Although the
disease is self-limiting, the risk to non-immune travellers from other
parts of the world to areas with a chikungunya epidemic,
continues to exist and should be included in the differential
diagnosis of travellers returning home with fever.
Due to
similarities in clinical presentation with dengue, limited awareness,
and a lack of laboratory diagnostic capability, CHIKV is probably
often underdiagnosed or misdiagnosed as
dengue
.
Treatment is
supportive. Analgesic and anticonvulsants are often used.
The prognosis
is generally good, although some patients experience chronic
arthritis. There are very few recorded fatalities.
With no
vaccine or antiviral available, prevention and control depends on
surveillance, early identification of outbreaks, and vector control.
CHIKV should
be borne in mind in sporadic cases, and in patients epidemiologically
linked to ongoing local or international outbreaks or endemic areas.
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