The "cliché" "an ounce of prevention is worth a pound of cure" means that preventing a disease is less costly economically and to the health of the host than treating the disease once it has occurred. Draw a flow chart (or list) showing the connections between reservoirs of infection; modes of transmission; host susceptibility factors, and portals of entry. These are the steps in the disease cycle that precede the infection of the host.  Are there ways of preventing host infection by halting the pathogen at these points? Discuss each step, and what measures can be used to eliminate the treat of potential disease at each point.