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Dengue fever virus
Last reviewed: 14.05.2024
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There are two independent clinical forms of this disease.
- Dengue fever, characterized by fever, severe pain in the muscles and joints, as well as leukopenia and the formation of lymphadenitis. Pain in the joints and muscles cause the patient to change the gait, this is what determined the name of the disease (English dandy - dandy).
- Hemorrhagic fever of dengue, for which in addition to fever are characterized by severe hemorrhagic diarrhea, shock and high lethality.
The causative agent of dengue fever and hemorrhagic fever of dengue is the same virus that was isolated and studied in 1945 by A. Sebin. This virus is similar in many respects to other flaviviruses. It has a spherical shape, the diameter of the virion is about 50 nm, on the surface of the supercapsid there are protrusions of 6-10 nm in length. The virus is pathogenic to newborn mice when infected inside the brain and into the abdominal cavity, as well as for monkeys; multiplies in the cultures of some transplanted cells. Has hemagglutination properties. It is sensitive to high temperature (rapidly inactivated at 56 ° C), ether, formalin and other disinfectants, but it is kept for a long time in a lyophilized state and at a temperature of -70 ° C.
Antigenic properties distinguish 4 serotypes (I-IV), which are differentiated well by the neutralization reaction.
[Pathogenesis and symptoms of dengue fever
At the heart of the pathogenesis of the disease is the violation of vascular permeability. As a result of water leakage, electrolytes and some plasma proteins, shock may occur. Hemorrhagic phenomena occur due to thrombocytopenia and defects in the blood coagulation system.
The hemorrhagic form of dengue fever, according to modern data, arises with repeated infection in a few months or years of persons previously afflicted with dengue, and necessarily another serotype. Violations of vascular permeability, activation of complement and other blood systems in this case are possible as a consequence of the damaging effect of the immune response. The dengue virus multiplies in various organs, but is most intense in the cells of a macrophage-monocyte system. Virus-infected macrophages synthesize and secrete a factor that changes the permeability of blood vessels; enzymes acting on the complement C3-component, blood coagulation system, etc. All this has an impact on the pathogenesis of the disease and the clinic of dengue fever and hemorrhagic dengue fever, which is characterized by wide variability.
The main difference between hemorrhagic fever and dengue fever is the development of shock dengue syndrome, which is the main cause of high lethality, sometimes reaching 30-50%.
Epidemiology of Dengue fever
The only reservoir of the virus is a person, and the main vector of the virus is mosquitoes Aedes aegypti, sometimes A. Albopictus. Therefore, the zones of foci of dengue fever coincide with the areas of these mosquitoes: the tropical and subtropical regions of Africa, Asia, America and Australia. There is evidence of the existence of a jungle variant of dengue fever in Malaysia, where the A. Niveus mosquito carries the virus, but this form has no significant epidemiological significance. The main role is played by the urban form of dengue fever. The epidemics of urban dengue in certain endemic areas are observed regularly and cover a large number of people.
Diagnosis of Dengue fever
To diagnose dengue fever, biological (intracerebral infection of 1-2-day white mice), virologic (infection of cell cultures) and serological methods are used. The growth of the titer of virus-specific antibodies is determined in paired sera with the help of RPGA, RSK, PH, IFM.