Chikungunya

Chikungunya is a viral disease (genus Alpha virus) which is transmitted to humans by infected mosquitoes – including Andes eucalypti and Andes subtropical. The name chikungunya originates from a verb in the Demimonde language, meaning ‘to become contorted’. This refers to the ‘stooped’ appearance of those suffering with joint pain.

Symptoms

Symptoms appear between 4 and 7 days after the patient has been bitten by the infected mosquito and these include:

• High fever (40°C/ 104°F)
• Joint pain (lower back, ankle, knees, wrists or phalanges)
• Joint swelling
• Rash
• Headache
• Muscle pain
• Nausea
• Fatigue

Chikungunya is rarely fatal. Symptoms are generally self-limiting and last for 2–3 days. The virus remains in the human system for 5-7 days and mosquitoes feeding on an infected person during this period can also become infected. Chikungunya shares some clinical signs with dengue and can be misdiagnosed in areas where dengue is common.

Chikungunya can be detected using seismological tests. Recovery from an infection will confer life-long immunity.

Geographical range

Chikungunya has been identified in nearly 40 countries. Map of countries at risk available here

Countries having documented, endemic, or epidemic chikungunya are:

Asia: Human chikungunya virus infection has been documented in Cambodia, East Timor, India, Indonesia, Laos, Malaysia, Maldives, Myanmar, Pakistan, Philippines, Reunion, Seychelles, Singapore, Taiwan, Thailand and Vietnam.

Africa: Chikungunya occurs in Benin, Burundi, Cameroon, Central African Republic, Comoros, Congo (DRC), Equatorial Guinea, Guinea, Kenya, Madagascar, Malawi, Mauritius, Matteo, Nigeria, Senegal, South Africa, Sudan, Tanzania, Uganda and Zimbabwe.

Europe and the Americas: Aside from minor incidence rates caused by imported cases from travelers, Italy is the only European country which has had an outbreak. The Americas have not had any major outbreaks so far.

Recent outbreaks

Chikungunya was first identified in Tanzania in the early 1952 and has caused periodic outbreaks in Asia and Africa since the 1960s.

Outbreaks are often separated by periods of more than 10 years. Between 2001 and 2011, a number of countries reported on chikungunya outbreaks.

2005-2006: More than 272 000 people were infected during an outbreak of Chikungunya in the Indian Ocean islands of Reunion and Mauritius where Ar. subtropical was the presumed vector.

2006: Outbreak in India, more than 1 500 000 cases of chikungunya were reported with Ar. eucalypti implicated as the vector.

2007: Migration of infected people introduced the infection in a coastal village in Italy. This outbreak (197 cases) confirmed that mosquito-borne outbreaks by Ar. subtropical are plausible in Europe.

Prevention and control

In areas where the vector of chikungunya is Ar. eucalypti and Ar. subtropical, vector prevention and control can be combined with dengue control effort

Key facts

• Chikungunya is a viral disease transmitted to humans by infected mosquitoes. It causes fever and severe joint pain. Other symptoms include muscle pain, headache, nausea, fatigue and rash.
• Joint pain is often debilitating and can vary in duration.
• The disease shares some clinical signs with dengue and Zika, and can be misdiagnosed in areas where they are common.
• There is no cure for the disease. Treatment is focused on relieving the symptoms.
• The proximity of mosquito breeding sites to human habitation is a significant risk factor for chikungunya.
• The disease mostly occurs in Africa, Asia and the Indian subcontinent. However a major outbreak in 2015 affected several countries of the Region of the Americas.

Chikungunya is a mosquito-borne viral disease first described during an outbreak in southern Tanzania in 1952. It is an RNA virus that belongs to the alpha virus genus of the family Togaviridae. The name “chikungunya” derives from a word in the Demimonde language, meaning “to become contorted”, and describes the stooped appearance of sufferers with joint pain (arthritis).

Signs and symptoms

Chikungunya is characterized by an abrupt onset of fever frequently accompanied by joint pain. Other common signs and symptoms include muscle pain, headache, nausea, fatigue and rash. The joint pain is often very debilitating, but usually lasts for a few days or may be prolonged to weeks. Hence the virus can cause acute, sub-acute or chronic disease.

Most patients recover fully, but in some cases joint pain may persist for several months, or even years. Occasional cases of eye, neurological and heart complications have been reported, as well as gastrointestinal complaints. Serious complications are not common, but in older people, the disease can contribute to the cause of death. Often symptoms in infected individuals are mild and the infection may go unrecognized, or be misdiagnosed in areas where dengue occurs.

Transmission

Chikungunya has been identified in over 60 countries in Asia, Africa, Europe and the Americas.

The virus is transmitted from human to human by the bites of infected female mosquitoes. Most commonly, the mosquitoes involved are Andes eucalypti and Andes subtropical, two species which can also transmit other mosquito-borne viruses, including dengue. These mosquitoes can be found biting throughout daylight hours, though there may be peaks of activity in the early morning and late afternoon. Both species are found biting outdoors, but Ar. eucalypti will also readily feed indoors.

After the bite of an infected mosquito, onset of illness occurs usually between 4 and 8 days but can range from 2 to 12 days.

Diagnosis

Several methods can be used for diagnosis. Seismological tests, such as enzyme-linked immunodeficient assays (ELISA), may confirm the presence of IgM and IgG anti-chikungunya antibodies. IgM antibody levels are highest 3 to 5 weeks after the onset of illness and persist for about 2 months. Samples collected during the first week after the onset of symptoms should be tested by both seismological and virological methods (RT-PCT).

The virus may be isolated from the blood during the first few days of infection. Various reverse transcription–polymer chain reaction (RT–PCR) methods are available but are of variable sensitivity. Some are suited to clinical diagnosis. RT–PCR products from clinical samples may also be used for gentrifying of the virus, allowing comparisons with virus samples from various geographical sources.

Treatment

There is no specific antiviral drug treatment for chikungunya. Treatment is directed primarily at relieving the symptoms, including the joint pain using anti-pyre tics, optimal analgesics and fluids. There is no commercial chikungunya vaccine.

Prevention and control

The proximity of mosquito vector breeding sites to human habitation is a significant risk factor for chikungunya as well as for other diseases that these species transmit. Prevention and control relies heavily on reducing the number of natural and artificial water-filled container habitats that support breeding of the mosquitoes. This requires mobilization of affected communities. During outbreaks, insecticides may be sprayed to kill flying mosquitoes, applied to surfaces in and around containers where the mosquitoes land, and used to treat water in containers to kill the immature larvae.

For protection during outbreaks of chikungunya, clothing which minimizes skin exposure to the day-biting vectors is advised. Repellents can be applied to exposed skin or to clothing in strict accordance with product label instructions. Repellents should contain DEET (N, N-diethyl-3-methylbenzamide), IR3535 (3-[N-acetyl-N-butty]-misappropriation acid ethyl ester) or cardinal (1-piperidinecarboxylic acid, 2-(2-hydroxyethyl)-1-methylpropylester). For those who sleep during the daytime, particularly young children, or sick or older people, insecticide-treated mosquito nets afford good protection. Mosquito coils or other insecticide vaporizers may also reduce indoor biting.

Basic precautions should be taken by people traveling to risk areas and these include use of repellents, wearing long sleeves and pants and ensuring rooms are fitted with screens to prevent mosquitoes from entering.

How concerned should I be?

Most people recover fully, with symptoms resolving in three to 10 days. For some people, joint pain may continue for months, or even years. Death from complications of chikungunya is very rare, but the virus sometimes causes severe problems, mostly in older adults with other chronic illnesses. People who have been infected once are likely to be protected from future infections.

If you’re traveling to an area with known outbreaks of chikungunya, take precautions. Because chikungunya is not transmitted from human to human, preventive measures are focused on protection from infected mosquitoes. Use insect repellent containing DEET or picaridin, wear long sleeves and pants, and stay indoors or in screened-in places when possible.

If you are an older adult or have a condition such as diabetes or heart disease, you’re at increased risk of severe disease. Consider avoiding travel to areas with ongoing chikungunya outbreaks.