Summary Common respiratory infections usually show a latent incubation period, followed by an acute stage. Finally, due to new synthesis of specific antibodies, the relative microorganisms undergo a massive eradication from hostile organism. Meanwhile, clinical symptoms induced by innate immunity mechanisms during these pathologies are assumed properly as host attempts for the expulsion of infectious agents. Some studies have demonstrated the existence of immuno-modulatory abilities by different infectious agents, which can inhibit inflammatory response and the development of respective symptoms by hostile organisms, especially during incubatory period. In contrast, after the incubatory period microorganisms-induced immuno-inhibitory effects may undergo a reduction, and in the meantime clinical symptoms appear a few days before the hostile organism synthesizes specific antibodies, which can eradicate these pathogens. From the evolutionary viewpoint of microorganisms, maybe induction of pathologic symptoms even before the period of specific hostile antibody synthesis, but not at beginning of infection, could play a particular adaptive role. Such scenario first could assure a maximal multiplication for the infectious agents, whereas later attempts to support the host abandonment, even due to induction of clinical expulsive symptoms. The existence of related pathologies since ancient times leads to the suggestion that perhaps the induction of such diseases is not a purpose per se for such pathogens, but rather an instrument to provide for host abandonment on time to catch a next one, assuring therefore maximal successive reproduction.