Chikungunya virus is an acute viral infectious disease with a transmissible transmission pathway caused by the arbovirus of the same name. A specific manifestation of fever is inflammation of the joints ‒ polyarthritis. The clinic of the disease is also characterized by high fever, symptoms of intoxication (weakness, fatigue, decreased performance, moderate headache) and rashes. Diagnosis of fever is based on the detection of the pathogen itself (chikungunya virus) and antibodies to it in human blood. Symptomatic treatment: antipyretic and analgesic drugs, antihistamines, vasoprotectors.
A92.0 Disease caused by Chikungunya virus
Chikungunya fever is a viral infection transmitted by the bite of mosquitoes belonging to the genus of snapper. It was first described in 1952 after an outbreak in Tanzania, at the same time the causative agent of fever was discovered. “Chikungunya” in one of the African dialects means “to be twisted”: due to severe arthralgia, the patient seeks to reduce pain by reducing voluntary movements – sometimes by fading in the most bizarre poses. This infection is relevant for the countries of Africa and Asia, the islands of the Indian Ocean. The number of new cases usually increases during the rainy season, especially among residents of agricultural areas, deaths are more often recorded in older people. On the European continent, in North and South America, fever occurs mainly in the form of imported cases.
The causative agent of infection is the RNA–containing chikungunya virus, classified as an arbovirus (transmitted by arthropod bite), a representative of the Togavirus family, the Alphavirus genus. Sources and reservoirs of infection are sick people, primates and some rodents, carriers are female mosquitoes of the genus Aedes. Depending on the species, these mosquitoes can inhabit and attack both outside (in the morning) and indoors (most often mosquitoes live in vases, pallets for flowers and plants, in bowls for feeding pets). A sick person does not pose a danger to others, but can serve as a source of infection of mosquitoes, and those of other people.
The predominant way of infection is transmissible (when bitten by a blood–sucking insect). There are assumptions that the transmission of the pathogen is possible when the blood of a sick person comes into contact with the blood of a healthy person (for example, with joint intravenous administration of narcotic drugs with one syringe, blood transfusion, the use of non-sterile instruments in a medical institution), but there are no reliable cases of such infection with chikungunya fever. The pathogen is unstable in the environment, dies under the action of high temperatures, ultraviolet light and conventional doses of disinfectants.
The pathogenesis of the disease has not been studied enough. It is believed that when bitten by a female mosquito, along with saliva, the chikungunya virus enters the human blood. The pathogen affects the vascular endothelium, in the cells of which it actively multiplies and accumulates, then penetrating into the bloodstream. The chikungunya virus shows a tropicity to the articular tissue, however, there is evidence of involvement in the pathological process of the heart muscle, digestive tract, eyes and brain. The lesion of the vascular wall increases its permeability, which leads to the release of plasma and shaped elements (mainly erythrocytes) into the tissue and is clinically manifested by hemorrhagic syndrome. The presence and intensity of immunity after infection is currently being investigated.
The incubation period is 4-8 days, in some cases it can be shortened to 2 days or lengthened to 12 days. The onset of the disease is always acute, sudden against the background of satisfactory well-being. A sharp increase in body temperature is characteristic, often immediately to high numbers (390C and above). Fever is accompanied by chills, sharp weakness, loss of appetite and muscle pain.
Pathognomonic is the occurrence of severe joint pain affecting small joints: wrists, feet, ankles, hands. The joints increase significantly in size, becoming almost motionless, and when trying to move, there is a sharp pain, somewhat decreasing at rest. To the touch, the joints are hot, swollen, with reddish skin above them. Characteristic of fever is the so‒called migrating polyarthritis – joint changes move from one limb to another, and the previous lesion disappears on its own.
Patients often complain of abdominal pain, stool breakdowns, nausea and rarely vomiting. On the skin of the upper half of the trunk, upper and lower extremities, patients have a papular (tubercular) rash with pronounced itching, which then passes with a slight peeling. Since the chikungunya virus pathologically changes the vascular wall, it is not uncommon for petechial (spot) rashes, gingival and nasal bleeding to occur.
In severe cases, bleeding from the gastrointestinal tract, genitourinary tract, hemorrhages in the retina and brain may occur. After recovery, joint stiffness may persist for a long time. Secondary bacterial infection is not excluded due to invasive methods of diagnosis and treatment (blood sampling, artificial ventilation, injections, installation of intravenous and urinary catheters), congestive pneumonia often develops. Fatal outcomes of fever are most often caused by late seeking medical help and the development of disseminated intravascular coagulation syndrome (DIC syndrome).
If chikungunya fever is suspected, it is mandatory to consult an infectious disease specialist, a dermatovenerologist and a therapist, if symptoms of eye and brain damage appear, an ophthalmologist and a neurologist. The basic diagnosis of infectious pathology includes laboratory and instrumental methods:
- Identification of infectious markers. From the very first days of the disease, it is possible to isolate the pathogen from the patient’s blood using PCR. By the ELISA method, a blood test for the presence of antibodies to the chikungunya virus is carried out in dynamics – at the patient’s request and after 14 days. To confirm the diagnosis, at least a twofold increase in the antibody titer is required.
- Clinical and biochemical blood tests. In the blood test, leukopenia and thrombocytopenia, acceleration of ESR, are observed when infected with the chikungunya virus. Biochemical indicators reflect an increase in the level of CRP, transaminase activity (ALT, AST), less often – an increase in bilirubin content.
- Radiation examination of joints. Ultrasound of the joints can reveal the presence of inflammatory changes, including articular effusion. Radiologically, joint damage in chikungunya fever has no pronounced morphological signs, therefore arthrography is used mainly to exclude other arthropathies.
Differential diagnosis is carried out with other hemorrhagic fevers (dengue, c, Crimean hemorrhagic, Lassa, Marburg and Ebola) and infections (influenza, leptospirosis, malaria, hepatitis B, typhus and paratyphoid). It is also necessary to exclude autoimmune vasculitis, oncological diseases, pneumonia, decompensation of diabetes mellitus, pyelonephritis, urolithiasis, sepsis, syphilis and rheumatoid arthritis.
Therapy is carried out in an infectious disease hospital. Recommended bed rest for up to 2-3 days of a steady decrease in body temperature, the use of mosquito nets over the bed, copious drinking and frequent fractional meals with the exception of fatty, fried foods, alcohol and seasonings. At this stage of the development of medicine, specific antiviral treatment of chikungunya fever has not been developed; the therapy of the disease is symptomatic (antipyretics, painkillers, antihistamines, drugs that strengthen the vascular wall). The use of aspirin and its analogues in this infectious pathology is prohibited due to the possible intensification of hemorrhagic syndrome.
Prognosis and prevention
The prognosis for timely detection of infection is favorable, various complications and deaths are more common in the weakened, elderly and children. In a population where there is no immunity to the disease and there are conditions for mass hatching and the existence of mosquitoes carrying the chikungunya virus, fever can be transmitted rapidly and affect a large number of healthy individuals (which is especially noticeable with annual outbreaks in African countries). With an uncomplicated course, the disease lasts about two weeks, while joint pain resolves independently in 80% of cases. In some patients, arthralgia may persist for more than six months after infection.
It is reported about the creation of a vaccine against chikungunya fever, but today the drug is still undergoing registration stages. In the future, the vaccine can be used to immunize people living in areas with high morbidity, as well as for people who want to visit them for tourist or work purposes. Non-specific prevention involves the fight against mosquitoes, timely detection and isolation of patients. Persons located in the habitats of disease vectors should use closed-type clothing, protective nets and repellents.