Rubella

Etiology and Epidemiology

The rubella pathogen belongs to the Togaviridae family, Rubivirus genus. The virus has only a single serotype and exhibits low environmental stability (rapidly destroyed by heat, UV irradiation, and disinfectants), yet it tolerates freezing well. Its key characteristic is high tropism for epithelial, lymphoid, neural, and embryonic tissues. The virus can suppress cellular mitotic activity and damage the chromosomal apparatus, which underlies its teratogenic effect.

The source of infection includes individuals with the manifest form (capable of shedding the virus for up to 1 year), asymptomatic carriers, and newborns with congenital rubella syndrome (prolonged shedding of the pathogen).

Main transmission routes:

• Aerogenic (airborne droplet route) — the primary route for the acquired form, requiring close contact.
• Vertical (transplacental route) — from an infected mother to the fetus.

Susceptibility to the infection is universal and very high. The only exception is infants in their first 6 months of life who are protected by innate passive immunity (maternal antibodies). The epidemic process is characterized by spring seasonality and cyclic morbidity peaks every 7–12 years.

Pathogenesis of acquired infection

The development of the disease goes through several consecutive stages:

1. Entry portal: the virus invades through the mucous membrane of the upper respiratory tract.
2. Primary replication: occurs in regional lymph nodes.
3. Viremia: on days 6–8, the pathogen breaks into the systemic circulation.
4. Target organ involvement: the virus attacks the vascular endothelium. This leads to increased vascular permeability, edema, and hemodynamic disturbances, which clinically manifest as catarrhal and intoxication syndromes.
5. Exanthema formation: the rash arises as a result of a focal inflammatory reaction in the endothelium of superficial skin capillaries.
6. Immune response: 2–3 days after the appearance of the rash, the synthesis of virus-neutralizing antibodies begins, ensuring viral elimination and the formation of lasting lifelong immunity.

Clinical presentation and syndromes

The incubation period lasts from 10 to 24 days. It is followed by a short prodromal period (1–2 days) characterized by low-grade fever (up to 38 °C), mild catarrhal syndrome (moderate faucial hyperemia), and enanthema on the mucosa.

Characteristics of the exanthema (rash): The rash in rubella is fine-spotted and pink. A crucial diagnostic sign is that the elements appear against a background of visually unchanged skin (erythema is absent) and have no tendency to merge. A rapid descending spread pattern is characteristic: starting on the face, the rash descends to the trunk and extremities within a few hours. The maximum concentration of elements is observed on the extensor surfaces of the extremities, back, and buttocks. The exanthema regresses without a trace in 1–3 days (without desquamation or pigmentation).

Lymphadenopathy syndrome: A typical sign is enlargement, induration, and tenderness of the lymph nodes (average diameter 0.6–1 cm). The occipital, posterior cervical, and parotid groups are predominantly affected. Lymphadenopathy can persist for several weeks.

In adults, rubella is significantly more severe: febrile fever (up to 38–39 °C), pronounced cephalalgia, myalgia, and loss of appetite are observed. Rare complications (more common in adults and older children) include polyarthritis (resolving within 1–2 weeks) and extremely severe rubella encephalitis (case fatality rate of 20–40%, which can develop either before or after the appearance of the rash).

Congenital rubella syndrome (CRS)

When a pregnant woman is infected, the virus crosses the placental barrier, damages the endothelium of placental capillaries (causing hypoxia), and disseminates throughout the fetal body. The greatest danger occurs with infection during the first 8 weeks of gestation, when interferon production is reduced in the embryo and cellular immunity is not yet formed. The suppression of mitotic activity leads to severe malformations or spontaneous abortion. In 75% of cases, combined lesions are observed.

Classical manifestations of CRS:

• Visual organs: cataracts (classical sign), glaucoma, chorioretinitis, microphthalmia.
• Cardiovascular system: congenital heart defects (patent ductus arteriosus, pulmonary stenosis, ventricular and atrial septal defects).
• Hearing organs: deafness.

Neonatal symptoms of intrauterine infection are also detected: low birth weight, hepatosplenomegaly, thrombocytopenia, anemia, and meningoencephalitis.

Diagnostics, treatment, and prevention

The diagnosis of a typical form is established clinically and epidemiologically. Laboratory diagnostics are mandatory for pregnant women, newborns, and atypical forms. ELISA (detection of specific IgM) or HAI/HI assays (assessment of antibody titer rise in paired sera with a 10-day interval) are used.

Treatment is not required in most cases. For complications, strictly symptomatic and pathogenetic therapy is prescribed.

Prevention: The basis of protection is vaccination with a live attenuated vaccine (subcutaneously or intramuscularly 0.5 ml). According to the Russian National Immunization Schedule, the first dose is administered at 12–15 months, and revaccination at 6 years (or at 13 years for unvaccinated girls). The strategic goal of immunization is to protect pregnant women from the wild-type strain. A normal post-vaccination reaction (from day 5 to 12) may include transient lymph node enlargement and a mild rash. In an infection focus, the patient is isolated for 5 days from the moment the rash appears. Contact children are observed for 21 days (without quarantine), while pregnant women are subject to strict isolation and serological monitoring.

Class and exam questions

What else to study on this topic

• Features of atypical and inapparent (asymptomatic) forms of rubella
• Differential diagnosis of rubella with measles and enteroviral exanthema
• Management algorithm for a pregnant woman after contact with a rubella patient
• Pathogenesis of the development of rubella encephalitis
• Interpretation of ELISA results (IgM and IgG) and the concept of "paired sera"

Other topics from the section «Chapter 12. Infectious and parasitic diseases»

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