An infectious disease

Chikungunya is an infectious disease caused by an arbovirus: the chikungunya virus.

This virus is transmitted from person to person primarily through bites from mosquitoes of the genus Aedes, mainly Aedes aegypti and Aedes albopictus (also known as the tiger mosquito). Chikungunya is an infectious disease caused by an arbovirus: the chikungunya virus. It belongs to the Togaviridae family (genus Alphavirus) and was first isolated in Uganda in 1953 during an epidemic in East Africa. The name chikungunya comes from the Makonde language and means “the man who walks bent over.”

The disease typically presents with fever and joint pain, which resolve spontaneously after a few days.

Several modes of transmission for chikungunya

Vector-borne transmission

The chikungunya virus is primarily transmitted by mosquito vectors. For this virus, the vectors are mosquitoes of the genus Aedes, mainly Aedes albopictus (also known as the tiger mosquito) and Aedes aegypti.
The chikungunya virus was first isolated in Tanzania in 1952. Chikungunya is an infection that is most prevalent in tropical and subtropical regions where the Aedes aegypti and Aedes albopictus vectors are present. Aedes albopictus is also found in temperate regions, particularly in Europe, including mainland France.
In France, Aedes aegypti is present in the French West Indies, French Guiana, and Mayotte, and Aedes albopictus is present on Réunion Island and in several metropolitan departments.

Aedes albopictus (also known as the tiger mosquito) is also present in southern Europe and in mainland France, where three transmission events have been identified. Two outbreaks, affecting several hundred patients, occurred in Italy in 2007 and 2017. These Aedes mosquitoes develop primarily in urban areas and do not move much during their lifetime. Females lay their eggs in breeding sites where stagnant water is necessary for larval development: pots, saucers, used tires, poorly drained gutters, various types of waste containing stagnant water, as well as tree hollows and certain plants that can retain water (bamboo, etc.). Man-made breeding sites are the primary locations where these mosquitoes lay their eggs.

Aedes bites occur mainly during the day, with peak activity at dawn and dusk. When biting an infected person in the viremic phase, the mosquito picks up the virus from that person’s blood. The virus then multiplies within the mosquito for approximately 10 days, known as the extrinsic phase. At the end of this extrinsic phase, the mosquito can transmit the virus and infect a new person during another bite.
For chikungunya, the viremic phase begins approximately 1 to 2 days before the onset of clinical symptoms and lasts up to 7 days afterward.

Transmission via human-derived products

The virus can, more rarely, be transmitted through transfusion or transplantation (of organs or cells).

Other modes of transmission

A few cases of mother-to-fetus (during the second trimester of pregnancy) and perinatal transmission have been documented

Symptoms and complications

In approximately 10 to 40% of cases, chikungunya is asymptomatic (percentage varies depending on the outbreak).
For the 60% to 90% of people who develop symptoms, the incubation period lasts an average of 3 to 7 days (up to 1 to 12 days). Typical symptoms include:

• A sudden onset of high fever

• Joint pain that can be severe, primarily affecting the small joints of the extremities (wrists, ankles, fingers)

• Muscle pain

• Headaches

• A maculopapular rash

The course is usually favorable after about ten days, with no lasting effects, but chikungunya can also progress to a chronic phase characterized by persistent joint pain. This can occur in 30 to 40% of patients and last for several months or even years in some patients. 

Diagnosis

Diagnosis of chikungunya virus infection is performed using techniques that may be direct (detection of the virus via culture or of its genome via PCR) or indirect (detection of antibodies via serology).

The diagnostic approach, recommended in the Ministry’s plan “Preventing the Spread of Chikungunya and Dengue in Metropolitan France,” is as follows:

• Up to 5 days after the onset of symptoms (Day 5): RT-PCR

• Between D5 and D7: RT-PCR and serology

• After D7: serology only (IgG and IgM) with a second confirmatory sample taken no earlier than 10 days after the first sample

Therefore, it is essential to accurately identify the date of symptom onset (DDS) in order to select the appropriate tests. Early testing (up to D7) using RT-PCR should be prioritized due to its higher specificity compared to serology. IgM antibodies
can be detected starting on the fifth day after the onset of clinical signs and persist for an average of 2 to 3 months. IgG antibodies appear a few days after IgM and persist for life.

Blood samples can be collected by any clinical laboratory. Each sample must be accompanied by a clinical information form. Laboratory
confirmation of chikungunya is particularly important in the French overseas departments and in mainland France where the vector (Aedes albopictus or Aedes aegypti) is established.

Prevention

Prevention relies on both individual and collective actions.

• Individual Prevention

Individual prevention relies on measures to protect against mosquito bites: repellents in sprays or creams, coil repellents, electric diffusers, long clothing, and mosquito nets. Protection is particularly necessary during the day, as Aedes vector mosquitoes bite mainly during the day, primarily outdoors, with peak activity in the early morning and late afternoon.

Two vaccines have recently received European marketing authorization: the IXCHIQ vaccine from Valneva and the VIMKUNYA vaccine from Bavarian Nordic.

As of April 10, 2025, the French National Authority for Health (HAS) issued recommendations for the use of the IXCHIQ vaccine in response to the epidemic situation on Réunion Island and the epidemic risk in Mayotte (published on March 5). This vaccine is recommended as a priority for people aged 65 and older (particularly those with comorbidities), followed by adults aged 18 to 64 with comorbidities, as well as exposed professionals, particularly vector control workers. The vaccine is contraindicated for immunocompromised individuals and not recommended for pregnant women. Vaccination of the populations covered by the recommendation began in Réunion on April 7. The HAS has also been consulted regarding the VIMKUNYA vaccine (recommendations pending). The HCSP has been asked to issue recommendations for chikungunya vaccination for travelers; these recommendations are currently being developed.

For more information:

• on the IXCHIQ vaccine

• about the VIMKUNYA vaccine

• vaccination strategy in Réunion and Mayotte | Haute Autorité de Santé

• vaccination against chikungunya | vaccination-info-service.fr

• Community-based prevention and vector control

Collective mosquito prevention and control also rely on vector control and community-based control.
The control of disease-carrying vectors, such as mosquitoes, is referred to as vector control. In its broadest sense, vector control encompasses both the control of and protection against these insects. Vector control relies on methods that vary depending on the vector and the epidemiological and socioeconomic contexts. It includes chemical control, biological control, genetic control, environmental interventions, health education, community mobilization, and the ongoing evaluation of all these methods.

Its objective is to contribute, alongside other public health initiatives, to reducing the risks of endemicity (the long-term establishment of a disease in a region) or epidemic outbreaks, to reducing the transmission of pathogens by vectors, and to managing outbreaks of vector-borne diseases, all within a formalized strategic framework.

Depending on the scale at which this mosquito control is carried out, a distinction is made between control at the regional level (departments, municipalities) and that carried out at the individual level, which specifically targets mosquito breeding sites located in the immediate vicinity of homes.

Vector control at the regional level is carried out by public mosquito control agencies. Chemical control has two components:

• Larvicides, which specifically target mosquito larvae

• Adulticide, which targets adult mosquitoes specifically

Community-based control, which is everyone’s responsibility, relies on:

• The elimination of potential larval breeding sites around homes (standing water in saucers, gutters, vases, buckets, trash, etc.)

• Personal protection against mosquito bites

Treatment

There is no specific antiviral treatment for chikungunya. Management is therefore primarily symptomatic, aimed at relieving symptoms. Pain and fever are treated with analgesics and antipyretics.
It is necessary to explain to the patient and their family and friends that mosquito protection measures help prevent transmission at home (see “How can the disease be prevented at the individual level?”). During the viremic phase of the disease, the patient must protect themselves from mosquito bites to prevent the mosquitoes from becoming infected and spreading the disease to those around them a few days later.

A Mosquito Established in Mainland France

Aedes albopictus (also known as the tiger mosquito) is considered the most invasive mosquito species in the world. It is native to Southeast Asia, from where it spread from east to west via commercial transport. In Europe, it was first identified in Albania in 1979 and then in Italy in 1990. It has been established in southern France since 2004 and has been gradually spreading ever since.

By early 2024, 78 departments had been colonized by the Aedes albopictus mosquito (out of the 96 metropolitan departments).