Structure and Antigenic Properties
RSV is a classic member of the genus Pneumovirus. Inside the polymorphic virion, which can be either spherical or filamentous, lies the genetic material — single-stranded helical negative-sense RNA.
Unlike many other paramyxoviruses, this pathogen completely lacks the surface enzymes hemagglutinin and neuraminidase. The outer lipoprotein envelope contains specific structural proteins that play a key role in the infectious process:
- Glycoprotein G — provides adhesion, meaning the binding of the virion to the receptors of a susceptible cell.
- Glycoprotein F (fusion) — is responsible for the fusion of the viral envelope with the cell membrane. This specific protein triggers the formation of the characteristic syncytium.
- SH protein (small hydrophobic) — functions as a transmembrane protein.
Its antigenic structure allows the virus to be divided into two main serogroups: A and B.
Epidemiology and Stability
The only source of infection in nature is an infected human. Transmission occurs via two main routes:
- Aerosol (classic droplet mechanism via coughing or sneezing).
- Contact-mediated (transmission via contaminated hands, household items, and linens).
Pathogen contagiousness is high, accounting for 3 to 16% of all registered acute respiratory infections (ARIs). The virus circulates actively in the population: by three years of age, 75% of children already have detectable protective virus-neutralizing antibodies (IgA).
Despite high infectivity, the virus is extremely unstable in the external environment. It is rapidly inactivated by standard physical and chemical factors.
Pathogenesis and Clinical Presentation
The portal of entry for the infection is the epithelium of the upper respiratory tract. Following the incubation period, the virus actively replicates in epithelial cells, leading to cell death.
The disease manifests as a typical ARI, but the infection tends to spread rapidly down into the lower respiratory tract, causing tracheobronchitis or pneumonia. The pathological process is aggravated by the formation of immune complexes, which trigger immunopathological reactions that enhance lung tissue damage. Concurrently, a secondary immunodeficiency develops against the background of the infection.
- Course of illness heavily depends on age. In older children and adults, RSV infection usually runs a mild course. However, for infants in their first six months of life, it poses a serious threat due to the high risk of respiratory failure.
Principles of Microbiological Diagnostics
To isolate the pathogen, nasopharyngeal secretions or lung tissue samples are sent to the laboratory. A strict pre-analytical rule: the test material must never be frozen.
The mainstay of diagnosis is the classic virological method — inoculation of cell cultures (e.g., continuous lines or primary monkey kidney cultures).
- Virus indication is carried out based on its specific cytopathic effect (CPE) — the formation of multinucleated cells (symplasts) and syncytia.
- Identification is performed using the neutralization test (NT), complement fixation test (CFT), or molecular genetic methods such as RT-PCR.