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What causes the catarrhal-respiratory syndrome?
Last reviewed: 19.10.2021
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Diseases accompanied by catarrhal respiratory syndrome are referred to the group of acute respiratory diseases (ARI). Most often their pathogens are viruses (ARVI). Less often - bacteria. The causes of catarrhal-respiratory syndrome - the action of allergic (with vasomotor rhinitis, hay fever) and irritants (for example, chlorine), a catarrhal factor. The combined effects of various factors are often expressed (for example, the cold factor and viruses, viruses and bacteria).
The main pathogens of ARI are viruses that have high trophicity to certain parts of the respiratory tract.
The total number of viruses (including their serotypes) that cause ARVI is more than 200. They cause more than 90% of cases of acute respiratory damage.
To the group of respiratory viruses include influenza and parainfluenza, adenoviruses, rhinoviruses, coronaviruses, enteroviruses. Almost all of them cause diseases with a similar clinical picture - catarrhal-respiratory syndrome on the background of severe symptoms of intoxication. Clinical manifestations of these diseases are due to both the properties of the virus and the immunoreactivity of the organism.
Clinically, the most significant SARS: influenza, parainfluenza, diseases caused by respiratory syncytial, adeno- and rhinoviruses, as well as coronaviruses.
The similarity of the clinical picture determines the single pathogenetic mechanisms in the development of ARVI:
- the introduction of an agent into the cells of the epithelium of the respiratory tract and its reproduction;
- viremia with the development of toxicosis and toxic-allergic reactions;
- development of the inflammatory process in the respiratory system;
- the reverse development of the infectious process, the formation of immunity.
The nature of the course of the infectious process is determined by a complex system of protective-adaptive reactions of the macroorganism aimed at limiting the reproduction of viruses and their elimination.
At the initial stage of the disease, the leading role belongs to factors of nonspecific defense, local IgA and phagocytosis, and specific cellular and humoral immunity - in the process of recovery.
Since the entrance gates in ARVI are the mucous membrane of the respiratory tract, local defense factors play a major role in preventing the development of the disease, among which macrophages and secretory immunoglobulins dominate (primarily IgA, which is able to prevent the adhesion of pathogens to the surface of epithelial cells and mediate the destruction and elimination of viruses) . When mucosal immunity is compromised, the viruses primarily affect the cells of the cylindrical epithelium of the respiratory tract. General pathomorphological changes in ARVI:
- cytoplasmic and intranuclear destruction of epithelial cells;
- a violation of the functional activity and integrity of the cilia and, consequently, mucociliary clearance;
- dystrophic changes in the epithelium and the possible appearance of serous or serous-hemorrhagic exudate in the lumen of the alveoli.
Although all respiratory viruses cause diseases with a similar clinical picture, characteristic features are revealed, which allow to assume with a reasonable probability the etiology of infectious disease.