Chikungunya fever is a viral disease caused by the chikungunya virus (CHIKV) which is transmitted to humans through the bite of an infected mosquito. CHIKV was first discovered during an epidemic in Tanzania in 1953, and has since been identified in west, central and southern Africa and many areas of Asia. The virus is present throughout much of Africa, with transmission thought to occur mainly between mosquitoes and monkeys.

What type of illness does chikungunya virus cause?

Chikungunya is a Makonde word (one of the local languages in Tanzania) meaning ‘that which bends up’, and describes the symptoms caused by the severe joint pains that usually accompany the infection. CHIKV infection can cause a debilitating illness, most often characterized by fever, headache, fatigue, nausea, vomiting, muscle pain, rash, and joint pain.

The illness typically starts from 3 to 7 days after a person is bitten by an infected mosquito, but it can sometimes take up to 12 days for symptoms to appear. “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 fever and some other mosquito-borne viral infections, some people experience fatigue or painful joints for many weeks after the initial infection.

Although CHIKV may occasionally cause severe infections in people, it is thought to be rarely if ever fatal.

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 people or animals such as monkeys which are infected with CHIKV.

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

Where does chikungunya virus occur?

Chikungunya occurs in Africa (more specifically west Africa from Senegal to Cameroon, central and east Africa including Central African Republic, Angola, Democratic Republic of Congo, Zambia, Zimbabwe, Tanzania, Malawi, Mozambique, eastern Botswana, and north eastern parts of South Africa; there is also evidence of viral presence in parts of Ethiopia and Sudan).

In Asia, chikungunya occurs in India, Sri Lanka, Thailand, Myanmar, Malaysia, Indonesia, and Cambodia. Outbreaks have also been seen in Saudi Arabia, Papua New Guinea, and more recently, on islands in the Indian Ocean, including Réunion, Comoros, Mauritius, and the Seychelles. In 2006 India experienced a large epidemic that affected a number of Indian States.

Given the current large CHIKV epidemics and the world-wide distribution of Aedes aegypti, there is also a risk of importation of CHIKV into new areas by infected travellers.

How is chikungunya virus infection treated?

No vaccine or specific antiviral treatment for chikungunya fever is available. Treatment is symptomatic – rest, fluids, and paracetamol may relieve symptoms of fever and aching. Aspirin should be avoided.

Infected persons should be protected from further mosquito exposure (staying indoors and/or under a mosquito net during the first few days of illness) so that they can't contribute to the transmission cycle.

Once a person has recovered with CHIKV infection they are likely to be immune from repeat infections.

What can people do to prevent becoming infected with chikungunya virus?

The best way to avoid CHIKV infection is to prevent mosquito bites. There is no vaccine or preventive drug against CHIKV.

Prevention tips are similar to those recommended for preventing dengue fever, a similar illness spread by mosquitoes:

apply insect repellent containing a DEET (diethyl toluamide) on exposed skin;
wear long sleeves and pants (ideally treat clothes with permethrin or another repellent);
ensure screens on windows and doors are secure and keep mosquitoes out; and
remove mosquito breeding sites by emptying standing water from around the home.

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