Factsheet for health professionals about chikungunya virus disease
Last reviewed: 28 April 2026
Disclaimer: The information contained in this factsheet is intended for general information and should not substitute individual expert advice or judgement of healthcare professionals.
Case definition
Chikungunya virus disease in humans is a notifiable disease at the EU/EEA level. The case definition is according to the Commission Implementing Decision (EU) 2018/945 of 22 June 2018 [1] .
The pathogen
Chikungunya virus (CHIKV) is a single-stranded positive-sense RNA enveloped virus from the Togaviridae family and the unique member of the species Alphavirus chikungunya. The virus belongs to the Semliki Forest virus serogroup that includes, amongst others, Ross River virus (in Australia and Pacific), Mayaro virus (MAYV, in Central and South America) and o’nyong-nyong virus (ONNV, in Africa).
There are three major genetically distinct lineages of CHIKV, all belonging to the same serotype. They reflected the geographical distribution (West Africa, East-Central-South Africa and Asia) until the spread of the East-Central-South African lineage to Asia in 2006 and the spread of the Asian type into the Americas in 2013.
The main vectors of CHIKV are Aedes (Ae.) aegypti and Ae. albopictus mosquito species. During the 2005-2006 outbreak in Réunion, France, an amino-acid change (A226V) in the E1 glycoprotein of East-Central-South African lineage CHIKV was identified. This change induced a gain of fitness for dissemination by Ae. albopictus mosquitoes [2]. Further mutations in E1 and E2 glycoproteins also modify mosquito infectivity [3]. CHIKV is a Risk Group 3 (RG-3) pathogen [4].
Clinical features and sequelae
The word ‘chikungunya’ means 'that which bends up', an allusion to the posture of suffering patients.
CHIKV infections can be acute, post-acute or chronic. Reported asymptomatic infection rates vary widely, generally ranging from 17% to 39% [5,6]; higher rates have occasionally been reported [7].
The incubation period ranges from 1 to 12 days (average: 3–7 days) [8]. Three clinical stages have been defined: acute stage (Day 1–21), post-acute stage (Day 21 to the end of month 3), and chronic stage (after 3 months) [9].
Within the acute stage, the initial febrile illness typically lasts around 10 days [9]. It is characterised by sudden onset of fever with chills, headache, myalgia, nausea and photophobia, together with incapacitating symmetric arthralgia and a petechial or maculopapular rash. Neurological, haemorrhagic and ocular manifestations have also been described [9].
In 60–70% of cases, symptoms persist beyond three weeks and may continue up to three months, corresponding to the post-acute stage [9].
The chronic stage is defined as the absence of return to the pre-existing condition more than three months after CHIKV disease onset and is characterised by recurrent joint pain [9]. It affects around 30–40% of those infected and can last from months to several years [9]. Risk factors for chronic symptoms include being female, over 45 years of age, and having comorbidities and pre-existing arthralgia [10-12]. In older adults, arthralgia can evolve into a chronic rheumatoid arthritis syndrome [9].
Complications are uncommon. They include myocarditis, hepatitis, ocular disease and neurological disorders (e.g. meningoencephalitis, acute disseminated encephalomyelitis, myelitis, Guillain-Barré syndrome and optic neuritis) [9]. CHIKV can also trigger decompensation of chronic cardiac, respiratory, renal, systemic (lupus) and other metabolic conditions (e.g., diabetes) [9]. Advanced age (>65 years) and comorbidities increase the risk of complications.
CHIKV infection does not appear to increase the risk of miscarriage, in utero foetal death or congenital conditions [13]. However, perinatal transmission can occur if the mother is viraemic during delivery [9,14]. Symptoms in neonates typically appear after a median incubation of four days and include fever, difficultly in breastfeeding, pain, thrombocytopenia and lymphopenia [9,15]. Severe disease (around 25% of newborns with an infection) may involve encephalopathy, cardiac involvement, haemodynamic failure and sepsis, and has been associated with long-term neurodevelopmental delay in about 50% of severe cases [9,16].
Despite being considered a non-fatal disease, sporadic deaths have been attributed to CHIKV disease. During the 2005-2006 outbreak in Réunion, France, the case fatality rate (CFR) potentially associated with CHIKV disease was 0.1% and increased markedly with age [17]. Overall, most deaths occurred in individuals with underlying medical conditions, such as chronic conditions, diabetes, cerebrovascular disease, and coronary heart disease [18]. During the CHIKV disease outbreak in Réunion, France, in 2024-2025, over 54 500 laboratory-confirmed cases were reported. Forty-five deaths were classified as CHIKV disease-related (i.e. CHIKV infection contributed to death), of which 22 were classified as directly linked to the disease (i.e. CHIKV was considered the direct cause of death) (CFR <0.01%). Among these deaths, two were neonates [19].
Epidemiology
CHIKV disease is a viral disease transmitted among humans by Aedes mosquitoes [20].
Humans are the major source and reservoir of CHIKV. However, in Africa, non-human primates bitten by forest-dwelling Aedes mosquitoes also serve as natural hosts [20]. The virus was first identified in Tanzania in 1953. Large-scale outbreaks were reported between 2004 and 2007 in Kenya, Comoros, Réunion (France), Mauritius, and then spread to various Indian states and Southeast Asia [21]. In December 2013, CHIKV was identified on the island of Saint Martin, France in the Caribbean, representing the first documented autochthonous transmission of the virus in the Americas [22]. Further epidemic circulation was quickly declared throughout the Americas, with nearly 1.2 million suspected and confirmed cases of CHIKV disease reported by February 2015 [23]. Today, the virus is endemic in sub-Saharan Africa, Southeast Asia, South Asia, the Pacific Region and tropical and subtropical regions of the Americas [21].
The disease is not endemic in mainland Europe despite the occurrence of several autochthonous transmission events during mosquito activity season. These events were the result of the introduction of the virus by travellers with an infection returning from affected areas.
In mainland Europe, the first autochthonous outbreak occurred in Italy in 2007, with 217 laboratory-confirmed cases [24]. This was the first outbreak reported in a non-tropical region where a competent vector for CHIKV was present.
Transmission
CHIKV is spread by the bite of Aedes mosquitoes, primarily Ae. aegypti (yellow fever mosquito) and Ae. albopictus (Asian tiger mosquito). These mosquitoes are active during the day, especially mid-morning and late afternoon to twilight). Both species are found biting outdoors, but Ae. aegypti will also bite indoors.
In humans, the viral load in the blood can be very high at the beginning of the illness and last 5-6 days (up to 10 days), allowing mosquitoes to feed and disseminate the virus.
Vertical transmission can occur when the mother is viraemic at delivery; caesarean sections do not appear to reduce this risk [9,25]. Around 50% of newborns contract an infection if delivery occurs from one day before to five days after onset of maternal symptoms [25]. There is no evidence of transmission through breast milk [26].
Once a person has recovered from CHIKV infection, acquired immunity is expected to be permanent.
Transmission of CHIKV through transfusion and transplantation has not been reported, although animal models using intravenous inoculation have demonstrated the ability of CHIKV to transmit the virus to the host via this route [27]. Additionally, CHIKV has been detected among asymptomatic blood donors during outbreaks [28-30]. Limited data suggest that the severity of clinical manifestations may correlate with the dose of CHIKV in the inoculum [31]. Furthermore, CHIKV has been isolated from corneo-scleral rims of potential corneal donors [32].
No evidence of sexual transmission of the virus has been reported, although the virus has been detected in semen and vaginal secretions [33,34]. A case of human-to-human transmission has been described in a healthcare worker after direct contact with a viraemic patient’s blood during haemostasis (bleeding control) following venipuncture [35].
Diagnostics
CHIKV infection can be detected using nucleic acid/genomic amplification techniques or viral isolation during the first week of illness [36,37]. The virus has been detected in several clinical samples, including urine, semen, saliva, breast milk, cerebrospinal fluid, amniotic fluid, biopsies (liver and brain) as well as in placenta [37]. Serological diagnosis can be performed by detection of specific IgM antibodies in serum or plasma specimens from day 4–5 after the onset of illness [36,37]. Specific IgM can persist for many months, in particular in patients with long-lasting arthralgia [38,39]. The phenomenon of cryoglobulinemia (with immunoglobulins precipitating when temperature is below 37°C) has been described as the cause of unexpected false-negative serology results, requiring pre-warming of sera before testing [40].
Serological cross-reactions between closely related alphaviruses have been reported [41,42]. These cross-reactions can lead to false-positive results in serological assays, as antibodies produced against one virus may react with antigens of a different, but structurally similar virus. This phenomenon has been particularly noted among CHIKV, o'nyong-nyong virus (ONNV), and Mayaro virus (MAYV), which are phylogenetically close and co-circulate in some regions (Americas for CHIKV and MAYV, Africa for CHIKV and ONNV) [37,41,42].
Case management and treatment
As no specific antiviral treatment is available, management of CHIKV disease is done through managing symptoms [9].
Public health prevention and control measures (for public health authorities)
Two vaccines have received marketing authorisation in the European Union:
- IXCHIQ® (Valneva) is a live attenuated vaccine authorised for use in individuals aged 12 years and older [43].
- VIMKUNYA (Bavarian Nordic) is a recombinant virus-like particle vaccine authorised for use in individuals aged 12 years and older [44].
An integrated vector management programme that sustainably reduces mosquito vector density is essential. Effective intersectoral collaboration and clear public communication are needed to support long-term community participation. At community level, key actions focus on reducing breeding sites by regularly draining, removing or discarding sources of standing water. This includes removing open containers with stagnant water in and around homes (e.g. plant saucers and pots, used tyres, tree holes and rock pools) and tightly covering water containers, barrels, wells and water storage tanks. Larvicides can be used where standing water cannot be removed or covered. During outbreaks, targeted adult mosquito control (e.g. aerial insecticide spraying) can also be considered.
More information on mosquito vectors of CHIKV can be found here: Aedes albopictus and Aedes aegypti.
Infection control, personal protection and prevention
Prevention is also based on individual protection against mosquito bites. Aedes mosquitoes bite during the day, both indoors and outdoors. Therefore, personal protection measures should be used throughout the day, especially during peak biting times (mid-morning and late afternoon to twilight). Personal protective measures include wearing clothing that covers most of the body and using mosquito repellent in accordance with the product label. Mosquito nets (preferably insecticide-treated nets) can be used while sleeping or resting (e.g. daytime naps), and staying in screened and/or air-conditioned rooms can further reduce exposure.
Advice to travellers
Disclaimer: Travel health physicians and travellers should always first consult national travel guidelines and recommendations as the primary source of information.
Travellers to areas where CHIKV is circulating should seek pre-travel health advice (e.g. from a travel clinic) to receive tailored recommendations on mosquito bite prevention and, where applicable, vaccination. This is parrticularly important for people at higher risk of severe outcomes, such as pregnant women, adults over 65 years of age, children, and people with immune disorders or severe chronic illnesses.
Travellers returning from areas with CHIKV transmission who live in locations in Europe where Ae. albopictus or Ae. aegypti is established should continue to protect themselves against mosquito bites for three weeks after return, to reduce the risk of transmitting the infection to local mosquitoes and triggering autochthonous transmission.
List of references
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