Chikungunya (CHIKV) fever, caused by Chikungunya virus, is an arboviral disease transmitted by the bite of the infected Aedes mosquitoes. The disease has affected millions of people and continues to cause epidemics in many countries. In late 2013, the first local (autochthonous) transmission in the Americas was documented.
Aedes albopictus is reported to be widely established and spreading in the Mediterranean basin from Spain to Greece. Recently it was found at places around the Black Sea coast (Bulgaria, Georgia, Romania, southern Russian Federation, and Turkey). A few mosquitoes have been detected in countries north of the Alps but their establishment has so far not been confirmed. Once the mosquito is established it is very difficult to eliminate.
The Ae. albopictus
Aedes aegypti was widespread in southern Europe until the early 1950s. Re-introductions are now occurring and the species is established on the island of Madeira and the north-eastern Black Sea coast. Aedes aegypti is closely associated with human habitation and uses the same artificial outdoor habitats as Ae. albopictus and occasionally indoor breeding sites, including flower vases, water storage vessels and concrete water tanks in bathrooms.
Both mosquitoes can be found biting throughout daylight hours, though there may be peaks of activity at dawn and dusk. Both species are found biting outdoors, but Ae. Aegypti will also readily feed indoors.
Humans serve as the primary CHIKV reservoir during epidemic periods. During inter-epidemic periods, several vertebrates have been implicated as potential reservoirs, including non-human primates, rodents, birds, and some small mammals.
Mosquitoes acquire the virus from a viremic host. Following an average extrinsic incubation of 10 days, the mosquito is then able to transmit the virus to a naïve host, such as a human. In humans bitten by an infected mosquito, disease symptoms typically occur after an average intrinsic incubation period of three to seven days (range: 1−12 days)
Following the bite of a mosquito infected with CHIKV, most individuals will present with symptomatic disease after an incubation period of three to seven days (range: 1−12 days). Not all individuals infected with the virus develop symptoms, however. Serosurveys indicate that between 3% and 28% of persons with antibodies to CHIKV have asymptomatic infections. Individuals acutely infected with CHIKV, whether clinically apparent or asymptomatic, can contribute to the spread of the disease if the vectors that transmit the virus are present and active in the same location.
CHIKV can cause acute, subacute, and chronic disease. Acute disease is most often characterized by sudden onset of high fever (typically greater than 102°F [39°C]) and severe joint pain. Other signs and symptoms may include headache, diffuse back pain, myalgias, nausea, vomiting, polyarthritis, rash, and conjunctivitis. The acute phase of CHIK lasts for 3−10 days.
Malaria: Periodicity of fever and alteration of consciousness
Dengue fever: Fever and two or more of the following, retro-orbital or ocular pain, headache, rash, myalgia, arthralgia, leucopenia, or hemorrhagic manifestations.
Leptospirosis: Severe myalgia localized to calf muscles with conjunctival congestion/or subconjunctival hemorrhage with or without jaundice or oliguria. Consider history of contact with contaminated water
Post-infectious arthritis (including rheumatic fever): Arthritis of one or more, typically larger joints due to an infectious disease such as Chlamydia, shigella, and gonorrhea. Rheumatic fever is seen more commonly in children as migratory polyarthritis predominantly affecting large joints. Consider antistreptolysin O (ASO) titer and history of sore throat with Jones criteria for rheumatic fever
Control the vector
At present, stopping the invasion of Aedes vector mosquitoes is the only method to prevent or control the transmission of Chikungunya virus. Prevention and control relies heavily on reducing the number of natural and artificial water-filled container habitats that support breeding of the mosquitoes.
During outbreaks, insecticides may be sprayed to kill flying mosquitoes, applied to surfaces in and around containers where the mosquitoes land, and used to treat water in containers to kill the immature larvae.
Stop spreading of the disease
In case chikungunya carrying mosquitoes establish in the environment, prevention of disease outbreaks should be prioritized. During outbreaks of chikungunya, clothing which minimizes skin exposure to the day-biting vectors is recommended. Repellents can be applied to exposed skin or to clothing in strict accordance with product label instructions. Repellents should contain DEET, IR3535 or icaridin. For those who sleep during daytime, particularly young children, or sick or older people, insecticide treated mosquito nets provide good protection. Mosquito coils or other insecticide vaporizers may also reduce indoor biting.
Effect on pregnancy
CHIK fever appears to have a direct impact on pregnancy with rare reports of spontaneous abortions and mother-to-child transmission in perinatal period.
Effect on neonates
Mothers afflicted with CHIK fever in the perinatal period (−4 days to +1 days before/after delivery) can transmit CHIK fever to neonates by vertical transmission. Caesarean section does not appear to prevent transmission. Neonatal CHIK fever is associated with fever, poor feeding, pain, distal edema, various skin manifestations, seizures, meningoencephalitis, and echocardiographic abnormalities in the newborn.
• There are no antiviral medicines to treat chikungunya
• There are medicines to help reduce the fever and pain
Illness course and outcomes
• Most patients feel better within a week
• Some people may develop longer-term joint pain
• People at increased risk for severe disease include newborns exposed during delivery, older adults (65 years and above), and people with medical conditions such as high blood pressure, diabetes, or heart disease
• Deaths are rare