Medical expert of the article
New publications
Rubella: causes and pathogenesis
Last reviewed: 23.04.2024
All iLive content is medically reviewed or fact checked to ensure as much factual accuracy as possible.
We have strict sourcing guidelines and only link to reputable media sites, academic research institutions and, whenever possible, medically peer reviewed studies. Note that the numbers in parentheses ([1], [2], etc.) are clickable links to these studies.
If you feel that any of our content is inaccurate, out-of-date, or otherwise questionable, please select it and press Ctrl + Enter.
Causes of rubella
The cause of rubella is a rubella virion of spherical shape, 60-70 nm in diameter, consists of an outer shell and a nucleocapsid. The genome is formed by an unsegmented molecule + RNA. The virion is antigenically homogeneous.
The rubella virus is sensitive to the action of chemical agents. It is inactivated by the action of ether, chloroform, formalin. At a temperature of 56 ° C perished in 30 minutes, at 100 ° C - after 2 minutes, when exposed to ultraviolet radiation - after 30 seconds. If there is a protein in the protein medium, the resistance of the virus increases. At low temperatures, the virus retains its biological activity well. The optimal pH for the virus is 6.8-8.1.
The virus contains a V- and S-soluble antigen exhibiting complement-binding activity.
The rubella virus can multiply in many kinds of primary and transplanted cultures of human tissue, monkey, rabbit, bull, poultry.
Virions form in the cytoplasm of a sensitive cell. The virus has a weak cytopathogenic effect, tends to form a chronic infection.
Reproduction of the rubella virus in tissue media is accompanied by the formation of interferon.
[1],
Pathogenesis of rubella
The site of primary replication of the virus is unknown, but already in the incubation period, viremia develops. And the virus is released into the environment with exhaled aerosol, urine and feces. The virus penetrates the body through the mucous membranes of the upper respiratory tract. Later, the virus multiplies in the lymph nodes (this process is accompanied by polyadenopathy), as well as in the skin epithelium, leading to the appearance of a rash. The virus penetrates the GEB and the placenta. As a result of activation of interferon production, formation of cellular and humoral immunity, the circulation of the virus stops and recovery comes, However, in pregnant women and children with congenital rubella virus can exist in the body for a long time.
With congenital rubella, the virus enters the fetus through the mother's bloodstream and infects the epithelium of villi chorion and the endothelium of the blood vessels of the placenta. Then enters the fetal bloodstream. In this case, organs and tissues are affected. Which are in the process of formation, i.e. In the so-called critical period of intrauterine development (for the brain this is the 3-11th week of pregnancy, for the eyes and the heart - for the 4th and 7th for the organ of hearing - 7-12th week). Psychomotor disorders of the fetus develop when the mother's disease rubella in the 3-4th month of pregnancy. Formed fetus is relatively resistant to the action of the virus. The frequency of the affected fetus depends on the period of pregnancy. Infection with rubella at the 1-4 th week of pregnancy leads to the defeat of the fetus in 60% of cases, at 9-12 weeks - in 15% of cases, at the 13-16th week - in 7% of cases. The earlier infection of the fetus occurred, the harder and more diverse its lesions. The development of vices and fetal anomalies is based on the ability of the virus to suppress the mitotic activity of cells and, to a lesser extent, its direct cytopathological effect.
Epidemiology of rubella
The source of the causative agent of rubella is sick, including those with an erased and atypical course of the disease, persons with asymptomatic infection and virus carriers. The virus is secreted from the mucus of the upper respiratory tract 1-2 weeks before the onset of the rash and within 3 weeks after the rash. In children with congenital rubella, the pathogen can be excreted from the body with urine, sputum, feces up to 2 years after birth.
The main route of transmission of the pathogen is airborne. Viralemia, which develops with rubella, determines the intrauterine way of transmission from mother to fetus, as well as the probability of parenteral transmission of the pathogen. The spread of the pathogen through the care items is of no practical significance.
Susceptibility to rubella is high. Immune to infection in children of the first half of life, if the mother has immunity to this infection. The most susceptible to rubella are children aged 1 to 9 years, most of whom do not have anti-redness immunity.
Postinfectious immunity to rubella in most cases is lifelong, repeated cases of the disease are extremely rare.
In rubella, various forms of the epidemic process are observed. For large cities, there is a constant incidence with seasonal winter-spring rises. There may be epidemic outbreaks, usually occurring at intervals of 7 years.
The incidence of rubella is characterized by a pronounced foci in children's groups. Rubella spreads there. Where people are in prolonged and close contact (family, school, kindergarten, hospital).