MAJOR EPIDEMIC AND PANDEMIC DISEASES
A number of communicable diseases can constitute significant threats at local, regional or global levels leading to epidemics or pandemics. An epidemic refers to an increase, often sudden, in the number of cases of an infectious disease above what is normally expected in a given population in a specific area. Examples of major epidemics include cholera and diarrhoeal diseases, measles, malaria, and dengue fever. A pandemic is an epidemic of infectious disease that spreads through human populations across a large region, multiple continents or globally. These are diseases that infect humans and can spread easily. Pandemics become disasters when they cause large numbers of deaths, as well as illness, and/or have severe social and economic impacts. Concerns exist about potential pandemic diseases including new strains of influenza, such as severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS) to which humans may not have immunity. In the past, pandemics have included cholera, smallpox, leprosy, measles, polio and yellow fever.