A pathogen has the possibility to attack the human body causing diseases or epidemics depending of our defenses. Government and control health organizations have an especial interest in to know what the probability of the human is and a population to be attacked and infected by the pathogens and how it can be influenced by the virulence and concentration of the external agent or substance. In this way, physics has been involved in the solution of the problem giving to the global health institutions a guide to control the disease, by understanding the situation as a quantum phenomenon known as penetration of a potential barrier or as classical diffusion problem which involves the spatial and temporal variation of the concentration of the pathogen that causes the disease. The computations required to the solution of this problem are presented with MAPLE and is expected that this solutions have important implications to the global health care.