Epidemiologic research shows that most diseases usually spread from one person to the other. This means that when one person in a population contracts a disease, the disease is likely to spread to others unless it is contained (Watts, 2003). For example, HIV is transmitted from one person another through body fluids, Malaria is spread from an infected person through mosquitoes, and many others. The medium of transmission however differs from disease to disease. Apart from the mode of transmission, there are other characteristics of each disease that determines their threat to others when one person is infected. These characteristics include infectivity, pathogenicity, virulence, toxigenicity, resistance, and antigenicity (Watts, 2003). Among these characteristics, the most significant ones when identifying diseases that place individuals in a given community a greater risk are toxigenicity, infectivity, and pathogenicity.