Chikungunya
The characteristics, symptoms, diagnosis and epidemiology of chikungunya.
Chikungunya is a mosquito-borne infection. It’s an alphavirus from the Togaviridae family, and was first isolated from patients during an epidemic in Tanzania in 1952.
The name chikungunya comes from a word in the Makonde language (one of the native languages in Tanzania) that means ‘that which bends up’, owing to the crippling pain in the joints caused by the virus.
Symptoms
Chikungunya is characterised by a sudden onset of fever usually accompanied by joint pain (arthralgia). However, symptoms can range from mild or non-existent to severe. It can often be misdiagnosed as other viral illnesses such as dengue fever in areas where these infections also occur.
Other common symptoms of chikungunya include:
- muscle pain
- headache
- nausea
- fatigue
- rash
The joint pain may be very debilitating, but usually ends within a few days or weeks.
Most patients make a full recovery. In some cases, joint pain and arthritis 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.
Transmission
The chikungunya virus is transmitted by the bite of an infected female Aedes mosquito. Aedes aegypti is most commonly associated with the transmission of chikungunya in tropical and sub-tropical regions, but Aedes albopictus (Asian tiger mosquito) has been associated with chikungunya transmission in more temperate regions, such as Italy.
When the mosquito feeds on the blood of a person infected with chikungunya, the virus enters and multiplies within the mosquito. After about 8 to 10 days, the mosquito can transmit the virus to another human, and can do this for the rest of its life.
Chikungunya is not spread directly from person to person. If a person acquires chikungunya abroad and becomes ill on their return to the UK, they can’t pass the infection onto anyone else. The Aedes mosquito is not present in the UK, as the temperature is not consistently high enough for it to breed.
After being bitten by an infected mosquito, it may take typically between 4 and 8 days for the first symptoms (usually fever and joint pain) to develop, but it can be shorter or longer in some people.
Diagnosis
Send the appropriate samples (with a full clinical and travel history) to Public Health England’s Rare and imported pathogens laboratory (RIPL). RIPL is a specialist centre for advice and diagnosis for a wide range of unusual viral and bacterial infections including chikungunya.
Treatment
There is no specific antiviral treatment for chikungunya. Supportive nursing care and relief of symptoms are the standard treatment.
Prevention
There is no vaccine or drug to prevent chikungunya.
The only way to prevent chikungunya is to avoid mosquito bites. Aedes mosquitoes bite during the day particularly around dawn and dusk (as opposed to mosquitoes that transmit malaria, which bite at night between dusk and dawn).
A good repellent containing N, N-diethylmetatoluamide (DEET) must be used on exposed skin, together with light cover-up clothing. If sunscreen is also being used, repellent must be applied after sunscreen. More information about insect bite avoidance is available from NaTHNaC.
In endemic areas, control programs rely on the elimination of mosquito breeding sites in the community by regular inspections and insecticide spraying of properties (particularly during an outbreak) and the education of local residents to regularly empty standing water and keep outside areas free from waste items in which water may collect.
Epidemiology
Chikungunya was first discovered in Africa although human infections remained at low numbers for several years.
In 2005, the African strain of chikungunya virus mutated and spread across the islands of the Indian Ocean, including Réunion, Mayotte, Mauritius, and the Seychelles, resulting in a major outbreak lasting several months that peaked in 2006.
In 2006 to 2007 the outbreak extended to India and has subsequently affected several other countries in South and South East Asia and the Pacific region.
A localised outbreak of chikungunya was reported in 2007 in the north east of Italy. This outbreak occurred as a result of an imported case from India.
In December 2013, chikungunya was detected for the first time in the Caribbean and by March 2015, over 1.25 million cases had been reported throughout the region of most islands and territories of the Caribbean and some parts of South and Central America.
In April 2014, an outbreak of chikungunya was reported in Tonga in the Pacific Ocean; several other islands in the Pacific region have also subsequently reported outbreaks.
In 2014, 11 locally-acquired cases have been reported in the South of France, likely as a result of an imported case from Cameroon.
Chikungunya in the UK
In recent years a small number of cases have been reported in England, Wales and Northern Ireland (EWNI) each year. Most have been acquired in the Indian sub-continent and South East Asia.
In 2014, 295 cases of chikungunya were reported in EWNI of which 88% had acquired their infection in the Caribbean and South America.
Annual report
Chikungunya: epidemiology in England, Wales and Northern Ireland.