Rubella virus

The rubella virus is the only representative of the genus Rubivirus belonging to the family of tobaccos.

Rubella (measles rubella) is an acute infectious disease characterized by spotty rashes on the skin, catarrh of the upper respiratory tract and conjunctiva, an increase in the cervical lymph nodes and signs of minor general intoxication.

The rubella virus is a typical representative of the togavirus family and is similar in appearance to alpha viruses. The virion is spherical, diameter about 60 nm, the genome is represented by a positive non-fragmented single-stranded RNA molecule with a molecular weight of 3 MD. The virus has a supercapsid, on the surface of which there are spikes of a glycoprotein nature 6-10 nm in length. There are two types of glycoproteins: E1 - has haemagglutinating properties in relation to avian red blood cells, and E2 - serves as a receptor when interacting with the cell. Both glycoproteins are protective antigens. There is only one serovar of the virus.

The virus is relatively unstable in the external environment, it is easily inactivated by fat solvents, detergents, at a pH below 5.0, at a temperature above 56 ° C. It is well preserved during freezing, especially at -70 ° C.

The rubella virus reproduces well and causes cytopathic changes in the cultures of human amnion cells, rabbit kidneys and Vero monkey kidneys. Degeneration occurs in the affected cells, giant multinucleate cells appear. In other cell cultures, the virus can reproduce without visible changes, but induces the development of interference that protects against the cytopathic effect of other viruses. This is the basis of the standard method for isolating the rubella virus, which consists in infecting the cells of a green monkey kidney with a test material and introducing into the culture 7-10 days of the ECHO virus type II or the virus of vesicular stomatitis. If cytopathic changes caused by the ECHO virus develop, therefore, the material does not contain the rubella virus, and conversely, the absence of the cytopathic effect of the ECHO virus indicates the presence of the rubella virus in the test material.

The rubella virus is pathogenic to humans, monkey macaques and rabbits. Other animals to the virus are insensitive.

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Pathogenesis and symptoms of rubella

Getting into the human body by airborne droplets, the virus first multiplies in the cervical lymph nodes. A week later, viremia develops, and a week later appears a rash that begins with the face and changes to the trunk and limbs. During this period, fever, an increase in other regional lymph nodes, joint pain (especially in adults) are possible. The rash usually lasts 2-3 days.

If the rubella is usually benign in children, in the form of a mild disease, in adults the course of the disease is quite severe, sometimes arthritis, encephalitis and thrombocytopenia develop. Rubella is particularly dangerous for women of childbearing age, as it can cause the congenital rubella syndrome (CRS), caused by the virus's ability to penetrate the placenta during the viremia and to exert a teratogenic effect on the growing fetus. This is due to the cytopathic effect of the virus on both dividing fetal cells and placental vessels. A consequence of this can be heart defects, deafness, congenital diseases of the eyes, microcephaly, spontaneous abortion, stillbirth,

Immunity

Virus neutralizing antibodies (IgM) appear in the blood during the manifestation of the rash, the maximum of their titer reaches 2-3 weeks, and after 2-3 months. They disappear. IgG appear after the disappearance of the rash and persist for a long time. Immunity after a childhood rubella is lifelong.

Epidemiology of rubella

Rubella is a typical anthroponotic airborne infection, highly contagious for those who do not have immunity. The peak of the incidence of rubella usually occurs in the spring. In the XX century. Epidemics were observed every 6-9 years, and after each epidemic in the next 5 years the incidence declined, and then again increased to the epidemic level 6-9 years after the last major outbreak. With rubella, the virus is released from the mucus of the nasopharynx and the upper respiratory tract in 1-2 weeks. Before the appearance of rash and within 2 to 3 weeks. After the onset of the rash. In utero infected children, the virus can be excreted in urine and feces within 1 to 1.5 years.

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Laboratory diagnosis of rubella

Diagnosis of rubella can be carried out by virological and serological methods. The material for virus isolation is nasopharyngeal discharge (in the presence of catarrhal phenomena) and blood before the appearance of the rash; blood, urine, excrements - after the appearance of the rash. The material is infected with cell cultures, the virus is identified in the RTGA, and also by the interference test. With congenital rubella, urine and feces are used as a test material for children.

Serological diagnosis of rubella determines antibodies of class IgM and IgG to the rubella virus in the blood with the help of RIF, IFM, RIM. Use paired sera, determine the rise of antibody titer.

Specific prevention and treatment of rubella

The main in the prevention of rubella - quarantine measures in children's groups. It is desirable to selectively immunize girls of 12-14 years of age, girls and women of childbearing age. For this purpose, live and killed vaccines obtained from attenuated strains of the virus, passaged at low temperature in the culture of kidney cells of green monkeys and diploid cells of the lungs of the human embryo are used for this purpose. There are associated drugs in combination with measles and mumps vaccines. WHO has set the goal of reducing the incidence of congenital rubella syndrome by 2010 to a level below 1 per 100,000 births by a live child. As already mentioned, a live trivalent vaccine is used for mass vaccination against measles, mumps and rubella.

There is no specific rubella treatment.