What role does infectious disease play in a pandemic?

Any disease caused by a microorganism that is capable of spreading through a population can be termed an infectious disease. An infectious disease is capable of spreading through the general environment by means such as airborne droplets and tainted water or contaminated personal items. Other diseases caused by microorganisms that spread by direct person-to-person contact are more accurately termed contagious diseases. Infectious diseases are often capable of spreading faster and affecting more individuals than are contagious diseases, though both types can and have caused pandemic outbreaks. Historically pandemics typically involve the outbreak of some specific infectious disease.