What is chikungunya fever?
Chikungunya fever is a viral disease transmitted to humans by the bite of infected mosquitoes. Chikungunya virus (CHIKV) is a member of the genus Alphavirus, in the family Togaviridae. CHIKV was first isolated from the blood of a febrile patient in Tanzania in 1953, and has since been identified repeatedly in west, central and southern Africa and many areas of Asia, and has been cited as the cause of numerous human epidemics in those areas since that time. The virus circulates throughout much of Africa, with transmission thought to occur mainly between mosquitoes and monkeys.

What type of illness does chikungunya virus cause?
CHIKV infection can cause a debilitating illness, most often characterized by fever, headache, fatigue, nausea, vomiting, muscle pain, rash, and joint pain. The term  "chikungunya" is thought to be derived from the word "kungunyala" in the Makonde language of southeastern Tanzania and northern Mozambique, which means "to dry up or become contorted".

The incubation period (time from infection to illness) can be 2-12 days, but is usually 3-7 days. "Silent" CHIKV infections (infections without illness) do occur; but how commonly this happens is not yet known.

Acute chikungunya fever typically lasts a few days to a couple of weeks, but as with dengue, West Nile fever, o'nyong-nyong fever and other arboviral fevers, some patients have prolonged fatigue lasting several weeks. Additionally some patients have reported
incapacitating joint pain, or arthritis which may last for weeks or months. The prolonged joint pain associated with CHIKV is not typical of dengue. Co-circulation of dengue fever in many areas may mean that chikungunya fever cases are sometimes clinically misdiagnosed as dengue infections, therefore the incidence of chikungunya fever could be much higher than what has been previously reported.

No deaths, neuroinvasive cases, or hemorrhagic cases related related to CHIKV infection have been conclusively documented in the scientific literature.

CHIKV infection (whether clinical or silent) is thought to confer life-long immunity.

How do humans become infected with chikungunya virus?
CHIKV is spread by the bite of an infected mosquito. Mosquitoes become infected when they feed on a person infected with CHIKV. Monkeys, and possibly other wild animals, may also serve as reservoirs of the virus. Infected mosquitoes can then spread the virus to other humans when they bite.

Aedes aegypti (the yellow fever mosquito), a household container breeder and aggressive daytime biter which is attracted to humans, is the primary vector of CHIKV to humans. Aedes albopictus (the Asian tiger mosquito)may also play a role in human transmission is Asia, and various forest-dwelling mosquito species in Africa have been found to be infected with the virus.

Where does chikungunya virus occur?
The geographic range of the virus is Africa and Asia. For information on current outbreaks, consult CDC's Travelers' Health. Given the current large CHIKV epidemics and the world wide distribution of Aedes aegypti, there is a risk of important of CHIKV into new areas by infected travelers.