ACUTE RESPIRATORY VIRAL INFECTIONS
The features of acute infectious diseases that distinguish them from others are specificity of the pathogen, contagiousness, cyclic nature, and subsequently, formation of immunity.
Acute respiratory viral infections (ARVI) are a group of diseases characterized by general symptoms of toxicosis and predominant lesion of the mucous membranes of the respiratory tract with airborne, possibly alimentary route of contamination. These include influenza, parainfluenza, adenovirus, rhinovirus, respiratory syncytial infections, some variants of enterovirus infections discovered in recent years - metapneu-moviruses, bocaviruses, etc. The number of viruses that cause ARVI reaches about two hundred.
The most powerful defense mechanism against acute respiratory viral infections is the mucous membrane, movement of ciliary epithelium of the mucous membrane of the upper respiratory tract, called ''mucociliary clearance'' (or ''transport''). The latter contributes to the destruction of all kinds of pathogenic viruses, bacteria, fungi, and when it is disturbed, acute respiratory viral infections develop (fig. 11.1).
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Fig. 11.1. Mechanism of lesion of the mucociliary system in viral infections
• ARVI hold the first place in prevalence in the world and make up 95% of all infectious diseases, with about 70% of them occurring in children.
• Children in the first months of life are less likely to get sick, the greatest morbidity occurs after six months and the first three years of life, which is associated with attending
a kindergarten and the like and, consequently, a drastic increase in the number of contacts.
• Influenza is associated with high mortality, especially in young children and the elderly.