What is the primary target of the influenza virus in humans?

The influenza virus primarily targets the respiratory epithelium in humans. This epithelial tissue lines the respiratory tract and is composed of cells that serve as the first line of defense against inhaled pathogens. When the virus infects these cells, it leads to damage and cell death, which disrupts normal respiratory function and triggers a cascade of immune responses. This infection is responsible for common symptoms associated with influenza, such as coughing, sore throat, and difficulty breathing.

In contrast, while the virus may have secondary effects on other systems such as the immune system or even the nervous system, these are not its primary targets. The initial attachment and infection rely heavily on the interaction between viral hemagglutinin proteins and sialic acid residues present on epithelial cells, underscoring the importance of the respiratory epithelium in the pathogenesis of influenza.