Pathophysiology
Aerosolized influenza virus is inhaled and embeds in the respiratory mucosa, of the upper and lower respiratory tract. The virus is attracted to the glycoproteins and mucopolysaccharides of the mucus coating the respiratory mucosa. If the infecting dose of virus is high, abundant viral neuraminidase breaks down the mucosal layer, allowing access of the virus to the underlying epithelial cells. The virus then attaches to epithelial cells through binding of the hemagglutinin spike to the N-acetylneuraminic acid receptor on the cell. The virus then enters the cell by endocytosis into the cell cytoplasm where it replicates to produce new virions that are released back into the respiratory tract by budding from the infected cell. The virus disperses throughout the trachea and bronchial tree within 3 days, causing hyperemia, edema, necrosis, desquamation, and focal erosion. Viremia is rare, but is possible if the virus crosses the basement membrane and enters the circulation, potentially causing inflammation of skeletal and cardiac muscle (myositis and myocarditis), encephalitic signs, and limb edema
Read more about this topic: Influenza A Virus Subtype H3N8