Chikungunya Chikungunya virus

Rash from chikungunya Cryoelectron microscopy
reconstruction of chikungunya
virus.From EMDB entry EMD-
5577[32]
Pronunciation Virus classification
Specialty
Group:Group IV ((+)ssRNA)
Symptoms Order:Unassigned
Complications
Family:Togaviridae
Usual onset Genus: Alphavirus
Duration Species: Chikungunya
virus
Causes Chikungunya virus (CHIKV)
spread by mosquitoes[3]
Diagnostic method
Blood test for viral RNA or antibodies[3]
Similar conditions
Dengue fever, Zika fever[3]
Prevention Mosquito control, avoidance of bites[4]
Treatment Supportive care[3]
Prognosis Risk of death ~ 1 in 1,000[4]
Frequency > 1 million (2014)[3]

Diagnosis[edit]
Chikungunya is diagnosed on the basis of clinical, epidemiological, and laboratory criteria. Clinically, acute onset of high fever and severe joint pain would lead to suspicion of chikungunya. Epidemiological criteria consist of whether the individual has traveled to or spent time in an area in which chikungunya is present within the last twelve days (i.e. the potential incubation period). Laboratory criteria include a decreased lymphocyte count consistent with viremia. However a definitive laboratory diagnosis can be accomplished through viral isolation, RT-PCR, or serological diagnosis.[54]
The differential diagnosis may include infection with other mosquito-borne viruses, such as dengue or malaria, and infection with influenza. Chronic recurrent polyarthralgia occurs in at least 20% of chikungunya patients one year after infection, whereas such symptoms are uncommon in dengue.[55]
Virus isolation provides the most definitive diagnosis, but takes one to two weeks for completion and must be carried out in biosafety level III laboratories.[56] The technique involves exposing specific cell lines to samples from whole blood and identifying chikungunya virus-specific responses. RT-PCR using nested primer pairs is used to amplify several chikungunya-specific genes from whole blood, generating thousands to millions of copies of the genes in order to identify them. RT-PCR can also be used to quantify the viral load in the blood. Using RT-PCR, diagnostic results can be available in one to two days.[56] Serological diagnosis requires a larger amount of blood than the other methods, and uses an ELISA assay to measure chikungunya-specific IgM levels in the blood serum. One advantage offered by serological diagnosis is that serum IgM is detectable from 5 days to months after the onset of symptoms, but drawbacks are that results may require two to three days, and false positives can occur with infection due to other related viruses, such as o'nyong'nyong virus and Semliki Forest virus.[56] casual and country style wears for a wedding
Presently, there is no specific way to test for chronic signs and symptoms associated with Chikungunya fever although nonspecific laboratory findings such as C reactive protein and elevated cytokines can correlate with disease activity.[57]
Prevention[edit]

A. aegypti mosquito biting a person
Because no approved vaccine exists, the most effective means of prevention are protection against contact with the disease-carrying mosquitoes and controlling mosquito populations by limiting their habitat.[4] Mosquito control focuses on eliminating the standing water where mosquitos lay eggs and develop as larva; if elimination of the standing water is not possible, insecticides or biological control agents can be added.[11] Methods of protection against contact with mosquitos include using insect repellents with substances such as DEET, icaridin, PMD (p-menthane-3,8-diol, a substance derived from the lemon eucalyptus tree), or IR3535. However, increasing insecticide resistance presents a challenge to chemical control methods.
Wearing bite-proof long sleeves and trousers also offers protection, and garments can be treated with pyrethroids, a class of insecticides that often has repellent properties. Vaporized pyrethroids (for example in mosquito coils) are also insect repellents. As infected mosquitos often feed and rest inside homes, securing screens on windows and doors will help to keep mosquitoes out of the house. In the case of the day-active A. aegypti and A. albopictus, however, this will have only a limited effect, since many contacts between the mosquitoes and humans occur outdoors.
Vaccine[edit]
As of 2017, no approved vaccines are available. A phase-II vaccine trial used a live, attenuated virus, to develop viral resistance in 98% of those tested after 28 days and 85% still showed resistance after one year.[58] However, 8% of people reported transient joint pain, and attenuation was found to be due to only two mutations in the E2 glycoprotein.[59]Alternative vaccine strategies have been developed, and show efficacy in mouse models.[60][61] In August 2014 researchers at the National Institute of Allergy and Infectious Diseases in the USA were testing an experimental vaccine which uses virus-like particles (VLPs) instead of attenuated virus. All the 25 people participated in this phase 1 trial developed strong immune responses.[62] Phase 2 trial will commence using 400 adults aged 18 to 60 and take place at 6 locations in the Caribbean.[63] Even with a vaccine, mosquito population control and bite prevention will be necessary to control chikungunya disease.[64]
Treatment[edit]
Currently, no specific treatment for chikungunya is available.[4] Supportive care is recommended, and symptomatic treatment of fever and joint swelling includes the use of nonsteroidal anti-inflammatory drugs such as naproxen, non-aspirin analgesics such as paracetamol (acetaminophen) and fluids.[4] Aspirin is not recommended due to the increased risk of bleeding.[65] Despite anti-inflammatory effects, corticosteroids are not recommended during the acute phase of disease, as they may cause immunosuppression and worsen infection.[10]
Passive immunotherapy has potential benefit in treatment of chikungunya. Studies in animals using passive immunotherapy have been effective, and clinical studies using passive immunotherapy in those particularly vulnerable to severe infection are currently in progress.[66] Passive immunotherapy involves administration of anti-CHIKV hyperimmune human intravenous antibodies (immunoglobulins) to those exposed to a high risk of chikungunya infection. No antiviral treatment for chikungunya virus is currently available, though testing has shown several medications to be effective in vitro.[8]
Chronic arthritis[edit]
In those who have more than two weeks of arthritis, ribavirin may be useful.[4] The effect of chloroquine is not clear.[4] It does not appear to help acute disease, but tentative evidence indicates it might help those with chronic arthritis.[4] Steroids do not appear to be an effective treatment.[4] NSAIDs and simple analgesics can be used to provide partial symptom relief in most cases. Methotrexate, a drug used in the treatment of rheumatoid arthritis, has been shown to have benefit in treating inflammatory polyarthritis resulting from chikungunya, though the drug mechanism for improving viral arthritis is unclear.[18]