Abstract- The immune system help to detect and eliminate most pathogens is essential for the survival of lower respiratory tract infection (Olubadeji, 2016). Lower respiratory tract infection (LRTI) constituted the second leading cause of death in all age bracket in Nigeria (Loddenkemper, 2013) Chronic lower respiratory diseases rank as the third leading cause of death in the United States (National Center for Health , 2015). The emerging and reemerging diseases have led to a revived interest in infectious diseases in which mathematical models have become important tools in analyzing the spread and control of infectious diseases. The model formation process clarifies assumptions, variables and parameters: moreover, a model provides conceptual results such as threshold and basic reproduction number. Mathematical models are used in comparing, planning, implementing, evaluating and optimizing various detection, prevention therapy and control programs. In this paper, we adopt the Passive Immunity Infant (M) � susceptible - Exposed-infected-recovered-susceptible (SEIRS) model to depict the spread of infections in our environment.