Host defenses

Repeated episodes of viral upper respiratory tract infections occur anywhere from four to eight times per year in healthy individuals Local and systemic defense mechanisms exist to battle respiratory tract pathogens. Clinical manifestations are mainly due to host inflammatory response. Unfortunately, the host defense mechanisms are very often not sufficient to prevent subsequent/repeated episodes of infections(s). Further insight into the interaction of infectious agent and host immune response, genetic factors, and environmental factors is needed for a better understanding of why humans repeatedly and frequently suffer from infections with respiratory agents and develop a disease syndrome known as common cold.