Chikungunya
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Chikungunya is an infection caused by the chikungunya virus.<ref name="WHO_FactSheet_2025">Template:Cite web</ref> The most common symptoms are fever and joint pain,<ref name="CDC_2024_Symptoms">Template:Cite web</ref> typically occurring four to eight days after the bite of an infected mosquito;<ref name="WHO_FactSheet_2025" /> however some people may be infected without showing any symptoms.<ref name="ECDC-factsheet-2024" /> Other symptoms may include headache, muscle pain, joint swelling, and a rash.<ref name="CDC_2024_Symptoms" /> Symptoms usually improve within a week; however, occasionally the joint pain may last for months or years.<ref name="CDC_2024_Symptoms" /><ref>Template:Cite journal</ref> The very young, old, and those with other health problems are at risk of more severe disease.<ref name="CDC_2024_Symptoms" />
The virus is spread between people by two species of mosquito in the Aedes genus: Aedes albopictus and Aedes aegypti,<ref name="WHO_FactSheet_2025" /> which mainly bite during the day,<ref>Template:Cite journal</ref><ref>Template:Cite web</ref> particularly around dawn and in the late afternoon.<ref>Template:Cite web</ref> The virus may circulate within a number of animals, including birds and rodents.<ref name="WHO_FactSheet_2025" /> Diagnosis is done by testing the blood for either viral RNA or antibodies to the virus.<ref name="WHO_FactSheet_2025" /> The symptoms can be mistaken for those of dengue fever and Zika fever, which are spread by the same mosquitoes.<ref name="WHO_FactSheet_2025" /> It is believed most people become immune after a single infection.<ref name="CDC_2024_Symptoms" />
The best means of prevention are overall mosquito control and the avoidance of bites in areas where the disease is common.<ref name="Caglioti-2013">Template:Cite journal</ref> This may be partly achieved by decreasing mosquitoes' access to water, as well as the use of insect repellent and mosquito nets. Chikungunya vaccines have been approved for use in the United States<ref name="FDA Approval-2023">Template:Cite press release</ref> and in the European Union.<ref>Template:Cite web</ref><ref>Template:Cite press release</ref><ref>Template:Cite web></ref> No specific treatment for chikungunya is available; supportive care is recommended, with symptomatic treatment of fever and joint swelling.<ref name="Caglioti-2013" />
The chikungunya virus is widespread in tropical and subtropical regions where warm climates and abundant populations of its mosquito vectors (A. aegypti and A. albopictus) facilitate its transmission.<ref name="WHO_FactSheet_2025" /> The disease was first identified in 1952 in Tanzania and named based on the Makonde words for "to become contorted".<ref name="WHO_FactSheet_2025" /> While the disease is endemic in Africa and Asia, outbreaks have been reported in Europe and the Americas since the 2000s.<ref name="WHO_FactSheet_2025" /> In 2014, more than a million suspected cases occurred globally.<ref name="WHO_FactSheet_2025" /> Chikungunya has become a global health concern due to its rapid geographic expansion, recurrent outbreaks, the lack of effective antiviral treatments, and potential to cause severe symptoms and death.<ref>Template:Cite journal</ref>
Signs and symptoms
Chikungunya can be asymptomatic, with estimates of between 17% and 40% of infections showing no symptoms.<ref name="ECDC-factsheet-2024" /> For those experiencing symptoms, they typically begin with a sudden high fever above Template:Convert around 3 to 7 days after the bite of an infected mosquito.<ref name="Burt_2017" /><ref name="ECDC-factsheet-2024" /> The fever is often accompanied by severe muscle and joint pain, which affects multiple joints in the arms and legs and is often symmetric – i.e. if one elbow is affected, the other is as well.<ref name="Vairo_2019">Template:Cite journal</ref><ref name="ECDC-factsheet-2024" /> People with chikungunya also frequently experience headaches, back pain, nausea, and fatigue.<ref name="Vairo_2019" /> Around half of those affected develop a rash, with reddening and sometimes small bumps on the palms, foot soles, torso, and face.<ref name="Vairo_2019" />
For some, the rash remains constrained to a small part of the body; for others, the rash can be extensive, covering more than 90% of the skin.<ref name="Burt_2017">Template:Cite journal</ref> Some people experience gastrointestinal issues, with abdominal pain and vomiting. Others experience eye problems, namely sensitivity to light, conjunctivitis, and pain behind the eye.<ref name="Vairo_2019" /> This first set of symptoms – called the "acute phase" of chikungunya – lasts around a week, after which most symptoms resolve on their own.<ref name="Vairo_2019" />
For those with severe symptoms, approximately 30% to 40% continue to have symptoms after the "acute phase" resolves.<ref name="ECDC-factsheet-2024" /><ref name="Vairo_2019" /> The lasting symptoms tend to be joint pains: arthritis, tenosynovitis, and/or bursitis.<ref name="Vairo_2019" /> If the affected person has pre-existing joint issues, these tend to worsen.<ref name="Vairo_2019" /> Overuse of a joint can result in painful swelling, stiffness, nerve damage, and neuropathic pain.<ref name="Vairo_2019" /> Typically the joint pain improves with time; however, the chronic stage can last anywhere from a few months to several years.<ref name="Vairo_2019" />
Almost all symptomatic cases feature joint pain, generally in more than one joint.<ref name="Thiberville-2013">Template:Cite journal</ref> Pain most commonly occurs in peripheral joints, such as the wrists, ankles, and joints of the hands and feet as well as some of the larger joints, typically the shoulders, elbows and knees.<ref name="Thiberville-2013" /><ref name="Burt-2012">Template:Cite journal</ref> Joints are more likely to be affected if they have previously been damaged by disorders such as arthritis.<ref name="Burt-2012" /> Pain may also occur in the muscles or ligaments. In more than half of cases, normal activity is limited by significant fatigue and pain.<ref name="Thiberville-2013" /> Infrequently, inflammation of the eyes may occur in the form of iridocyclitis, or uveitis, and retinal lesions may occur.<ref>Template:Cite journal</ref> Temporary damage to the liver may occur.<ref>Template:Cite journal</ref>
People with chikungunya occasionally develop long term neurologic disorders, most frequently swelling or degeneration of the brain, inflammation or degeneration of the myelin sheaths around neurons, Guillain–Barré syndrome, acute disseminated encephalomyelitis, hypotonia (in newborns), and issues with visual processing.<ref name="Vairo_2019" />
Newborns, the elderly, and those with diabetes, heart disease, liver and kidney diseases, and human immunodeficiency virus infection tend to have more severe cases of chikungunya. Fewer than 1 in 1,000 people with symptomatic chikungunya die of the disease; generally these are people with pre-existing health conditions.<ref name="Vairo_2019" /><ref name="ECDC-factsheet-2024" />
Transmission
Chikungunya is generally transmitted from mosquitoes to humans. Chikungunya is spread through bites from Aedes mosquitoes, specifically A. aegypti (Egyptian mosquito) and A. albopictus (Tiger mosquito).<ref name="WHO_FactSheet_2025" /> Because high amounts of virus are present in the blood during the first few days of infection, the virus can spread from an infected human to a mosquito, where it replicates without harming the mosquito. Subsequently, a bite from the infected mosquito will transmit the virus back to a human.<ref name="WHO_FactSheet_2025" /> The incubation period ranges from one to twelve days and is most typically three to seven.<ref name="Thiberville-2013" />
Rarely, the disease can be transmitted from mother to child during pregnancy or at birth, in women who become infected a few days before delivery.<ref name="ECDC-factsheet-2024" />
Mechanism
Chikungunya virus is passed to humans when a bite from an infected mosquito breaks the skin and introduces the virus into the body. The virus initially replicates in cells near the location of the bite; from here it enters the lymphatic system and the bloodstream, enabling it to circulate to organs and tissues which become infected. Most frequently it reproduces in the lymphatic system and the spleen, as well as peripheral joints, muscles and tendons where symptoms frequently occur; it appears that the virus is able to penetrate and replicate in many different types of cells.<ref name=":12">Template:Cite journal</ref> In severe cases it can infect the brain and liver.<ref name=":0">Template:Cite journal</ref><ref name=":12" />
During the acute phase of infection, large numbers of infectious virus particles are present in the bloodstream, making it very likely that an uninfected mosquito will pick up the virus if it bites the human host.<ref name=":0" /> <ref name=":12" />
During the first few days of infection, the host's innate immune system is activated, producing type I interferons and inflammatory cytokines to fight the infection. This generates the fever and localised inflammation which is characteristic of the disease.<ref name=":12" /><ref name=":3">Template:Cite journal</ref> It takes about a week before the host's adaptive immune system begins to develop antibodies which eventually clear the virus from the bloodstream.<ref>Template:Cite web</ref> However the virus can persist within specific tissues, especially the joints, causing long term inflammation and pain in chronic cases.<ref name=":3" />
The virus has mechanisms which help it to evade the immune response. Within an infected cell, the viral nonstructural protein 2 (nsP2) interferes with the JAK-STAT signalling pathway to hinder it from triggering an antiviral response.<ref>Template:Cite journal</ref> The virus can induce apoptosis (programmed cell death) in host cells; virus laden debris from apoptosis is engulfed by macrophages which in turn become infected.<ref>Template:Cite journal</ref> The virus also seems to be able to evade T lymphocytes which seek to target and destroy the virus particles.<ref>Template:Cite journal</ref>
Diagnosis
Diagnosing chikungunya can be difficult because its symptoms, such as sudden fever and joint pain, closely resemble other mosquito-borne illnesses like dengue fever and malaria.<ref name=":1">Template:Citation</ref> Chikungunya should be suspected if a patient with these symptoms either lives in an area where the virus is endemic, or if f they have recently traveled to such an area.<ref name=":1" /><ref name="CDC_2024_About">Template:Cite web</ref>
During the first week of illness, when virus is present in the bloodstream, it is possible to detect viral RNA in a blood sample using techniques such as reverse transcription-polymerase chain reaction (RT-PCR) or viral culture.<ref name="CDC_2024_About" /> After this time, the body develops antibodies and the virus is eliminated from the bloodstream. Antibodies in blood serum persist for between 3 and 12 months; they can be detected for up to a year after infection using enzyme-linked immunosorbent assay (ELISA) or indirect fluorescent antibody (IFA).<ref name=":1" /><ref name="Vairo_20192">Template:Cite journal</ref> All of these techniques are time consuming and costly, requiring sophisticated laboratory equipment which may not be available in resource poor settings.<ref>Template:Cite journal</ref>
Differential diagnosis
The Aedes mosquitoes which carry chikungunya virus can also carry other viruses such as dengue, zika, and yellow fever.<ref name=":2">Template:Cite journal</ref> Other infections which should be considered include malaria, leptospirosis, measles, mononucleosis and African tick bite fever, which are often endemic in the same areas and can have similar symptoms. It is possible for a patient to be infected by more than one virus simultaneously.<ref name=":1" />
Prevention
Although an approved vaccine exists, the most effective means of prevention is to avoid or prevent mosquito bites. The main strategies for this are: controlling mosquito populations by limiting their habitat; and protection against contact with disease-carrying mosquitoes.<ref name="Caglioti-2013" /> On a large scale, mosquito control focuses on eliminating standing water where mosquitoes lay eggs and develop as larvae.<ref name="Weaver-2015">Template:Cite journal</ref> Individuals should use mosquito repellent, as well as barriers such as loose clothing that covers the arms and legs, mosquito nets and window and door screens.<ref>Template:Cite web</ref>
Once immunity against chikungunya has been acquired, whether as a result of infection or vaccination, it endures long term and may be lifelong.<ref name="ECDC-factsheet-2024" /><ref>Template:Cite web</ref>
Vaccination
Treatment
No specific treatment for chikungunya is available.<ref name="Caglioti-2013" /> Supportive care is recommended, and symptomatic treatment of fever and joint swelling includes the use of paracetamol (acetaminophen), rest, and fluids.<ref name="Caglioti-2013" /><ref name="ECDC-factsheet-2024">Template:Cite web</ref> Non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin or ibuprofen should not be used in the acute phase until dengue fever has been ruled out, as these can increase the risk of bleeding in dengue.<ref name="WHO_FactSheet_2025" /><ref name=":1" />
Chronic symptoms, especially joint pain, may persist for months after the infection has passed. The pain and swelling may be treated with NSAIDs or in more severe cases with corticosteroid drugs or disease-modifying antirheumatic drugs such as hydroxychloroquine.<ref name=":1" /><ref>Template:Cite journal</ref>
Prognosis
The mortality rate of chikungunya is slightly less than 1 in 1000.<ref name="Mavalankar-2008">Template:Cite journal</ref> Those over the age of 65, infants, and those with underlying chronic medical problems are most likely to have severe complications.<ref name="Morrison-2014">Template:Cite journal</ref> Newborn infants are especially vulnerable as they lack fully developed immune systems, and may pick up the infection through vertical transmission from their mother.<ref name="Morrison-2014" /> The likelihood of prolonged symptoms or chronic joint pain is increased with increased age and prior rheumatological disease.<ref name="Schilte-2013">Template:Cite journalTemplate:Open access</ref><ref name="Gérardin-2013">Template:Cite journal</ref>
Epidemiology
Historically, chikungunya has been present mostly in the developing world. The disease causes an estimated 3 million infections each year.<ref>Template:Cite news</ref> Epidemics in the Indian Ocean, Pacific Islands, and in the Americas, continue to change the distribution of the disease.<ref name="Sam-2012">Template:Cite journal</ref> In Africa, chikungunya is spread by a sylvatic cycle in which the virus largely cycles between other non-human primates, small mammals, and mosquitos between human outbreaks.<ref name="Powers-2007">Template:Cite journal</ref>
During outbreaks, due to the high concentration of virus in the blood of those in the acute phase of infection, the virus can circulate from humans to mosquitoes and back to humans.<ref name="Powers-2007" /> The transmission of the pathogen between humans and mosquitoes that exist in urban environments was established on multiple occasions from strains occurring on the eastern half of Africa in non-human primate hosts.<ref name="Weaver-2015" /> This emergence and spread beyond Africa may have started as early as the 18th century.<ref name="Weaver-2015" />
Available data does not indicate whether the introduction of chikungunya into Asia occurred in the 19th century or more recently, but this epidemic Asian strain causes outbreaks in India and continues to circulate in Southeast Asia.<ref name="Weaver-2015" /> In Africa, outbreaks were typically tied to heavy rainfall causing increased mosquito population. In recent outbreaks in urban centers, the virus has spread by circulating between humans and mosquitoes.<ref name="Burt-2012" />
Global rates of chikungunya infection are variable, depending on outbreaks. When chikungunya was first identified in 1952, it had a low-level circulation in West Africa, with infection rates linked to rainfall. Beginning in the 1960s, periodic outbreaks were documented in Asia and Africa. Since 2005, following several decades of relative inactivity, chikungunya has re-emerged and caused large outbreaks in Africa, Asia, and the Americas. In India, for instance, chikungunya re-appeared following 32 years of absence of viral activity.<ref name="Lahariya-2006">Template:Cite journal</ref>
Outbreaks have occurred in Europe, the Caribbean, and South America, areas in which chikungunya was not previously transmitted. Local transmission has also occurred in the United States and Australia, countries in which the virus was previously unknown.<ref name="Burt-2012" /> In 2005, an outbreak on the island of Réunion was the largest then documented, with an estimated 266,000 cases on an island with a population of approximately 770,000.<ref name="Roth-2014">Template:Cite journal</ref> In a 2006 outbreak, India reported 1.25 million suspected cases.<ref name="Muniaraj-2014">Template:Cite journal</ref>
Chikungunya was introduced to the Americas in 2013, first detected on the French island of Saint Martin,<ref>Template:Cite news</ref> and for the next two years in the Americas, 1,118,763 suspected cases and 24,682 confirmed cases were reported by the PAHO.<ref>Template:Cite web</ref> In 2023, Brazil experienced a significant outbreak, with over 180,000 cases reported, prompting intensified public health interventions and renewed research efforts on viral mutations and transmission patterns<ref>Template:Cite journal</ref>
An analysis of the genetic code of chikungunya virus suggests that the increased severity of the 2005–present outbreak may be due to a change in the genetic sequence which altered the E1 segment of the virus' viral coat protein, a variant called E1-A226V. This mutation potentially allows the virus to multiply more easily in mosquito cells.<ref name="Schuffenecker-2006">Template:Cite journal</ref> The change allows the virus to use Aedes albopictus as a vector in addition to the more strictly tropical main vector, Aedes aegypti.<ref>Template:Cite journal Template:Open access</ref> Enhanced transmission of chikungunya virus by A. albopictus could mean an increased risk for outbreaks in other areas where the mosquito is present.<ref>Template:Cite journal</ref> A. albopictus is an invasive species which since the 1960's has spread through Europe, the Americas, the Caribbean, Africa, and the Middle East.<ref>Template:Cite web</ref>
After the detection of zika virus in Brazil in April 2015, the first ever in the Western Hemisphere,<ref>Template:Cite web</ref><ref>Template:Cite web</ref> it is nowTemplate:When thought some chikungunya and dengue cases could in fact be zika virus cases or coinfections.Template:Cn
Since the start of 2025, and as of 25 February, more than 30,000 chikungunya virus cases and 14 related deaths have been reported across 14 countries and territories in the Americas, Africa, Asia, and Europe.<ref>Template:Cite web</ref>
History
The disease was first described by Marion Robinson<ref name="Robinson-1955">Template:Cite journal</ref> and W.H.R. Lumsden<ref name="Lumsden-1955">Template:Cite journal</ref> in a pair of 1955 papers, following an outbreak in 1952 on the Makonde Plateau, along the border between Mozambique and Tanganyika (the mainland part of modern-day Tanzania). Since then outbreaks have occurred occasionally in Africa, South Asia, and Southeast Asia; recent outbreaks have spread the disease over a wider range.Template:Citation needed
The first recorded outbreak may have been in 1779.<ref name="Carey-1971">Template:Cite journal</ref>
According to the original paper by Lumsden, the term 'chikungunya' is derived from the Makonde root verb kungunyala, meaning to dry up or become contorted. In concurrent research, RobinsonTemplate:Citation needed glossed the Makonde term more specifically as "that which bends up". It is understood to refer to the contorted posture of people affected with severe joint pain and arthritic symptoms associated with this disease.<ref>Template:Cite journal</ref> Subsequent authors overlooked the references to the Makonde language and assumed the term to have been derived from Swahili, the lingua franca of the region and part of a different branch of Bantu languages. The erroneous attribution to Swahili has been repeated in numerous print sources.<ref>Template:Cite web</ref>
In July 2025, a severe outbreak occurred in China's Guangdong province. Seven thousand people tested positive for the disease, although symptoms were said to be minor for 95% of those people.<ref>Template:Cite web</ref>
Research
Chikungunya is one of more than a dozen agents researched as a potential biological weapon.<ref name="James_Martin_2002">"Chemical and Biological Weapons: Possession and Programs Past and Present Template:Webarchive", James Martin Center for Nonproliferation Studies, Middlebury College, 9 April 2002, accessed 18 June 2014.</ref><ref>Template:Cite web</ref>
This disease is part of the group of neglected tropical diseases.<ref>Template:Cite web</ref>
Chikungunya virus
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Virology
Chikungunya virus is a member of the genus Alphavirus, and family Togaviridae. Chikungunya virus features an icosahedral capsid surrounded by a lipid envelope, with a diameter ranging from 60 to 70 nm.<ref>Template:Cite journal</ref> It was first isolated in 1953 in Tanzania and is an RNA virus with a positive-sense single-stranded genome of about 11.6kb.<ref name="Weaver-2012">Template:Cite journal</ref> It is a member of the Semliki Forest virus complex and is closely related to Ross River virus, O'nyong'nyong virus, and Semliki Forest virus.<ref>Template:Cite journal</ref> Because it is transmitted by arthropods, namely mosquitoes, it can also be referred to as an arbovirus (arthropod-borne virus). In the United States, it is classified as a category B priority pathogen,<ref>Template:Cite web</ref> and work requires biosafety level III precautions.<ref>Template:Cite web</ref>
Three genotypes of this virus have been described, each with a distinct genotype and antigenic character: West African, East/Central/South African, and Asian genotypes.<ref name="Powers-2000">Template:Cite journal</ref> The Asian lineage originated in 1952 and has subsequently split into two lineages – India (Indian Ocean Lineage) and South East Asian clades. This virus was first reported in the Americas in 2014. Phylogenetic investigations have shown two strains in Brazil – the Asian and East/Central/South African types – and that the Asian strain arrived in the Caribbean (most likely from Oceania) in about March 2013.<ref name="Sahadeo-2017">Template:Cite journal</ref> The rate of molecular evolution was estimated to have a mean rate of 5 × 10−4 substitutions per site per year (95% higher probability density 2.9–7.9 × 10−4).<ref name="Sahadeo-2017" />
The chikungunya virus genome encodes both structural and non-structural proteins as typical of alphavirus genomic organization.<ref name="Wang-2024">Template:Cite journal</ref> The structural proteins, including the capsid, E3, E2, 6K and E1, are responsible for encapsulating the viral genome and assembling new viral particles. These proteins are critical for viral entry into host cells. Meanwhile, the non-structural proteins, nsP1, nsP2, nsP3, and nsP4, play essential roles in viral replication, translation, and immune evasion.<ref name="Wang-2024" />
Viral replication
The virus consists of four nonstructural proteins and three structural proteins.<ref name="Weaver-2015" /> The structural proteins are the capsid and two envelope glycoproteins: E1 and E2, which form heterodimeric spikes on the viron surface. E2 binds to cellular receptors in order to enter the host cell through receptor-mediated endocytosis. E1 contains a fusion peptide which, when exposed to the acidity of the endosome in eukaryotic cells, dissociates from E2 and initiates membrane fusion that allows the release of nucleocapsids into the host cytoplasm, promoting infection.<ref>Template:Cite journal</ref> The mature virion contains 240 heterodimeric spikes of E2/E1, which after release, bud on the surface of the infected cell, where they are released by exocytosis to infect other cells.<ref name="Weaver-2012" />
See also
References
External links
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