The word epidemic is derived from the Greek words epi (on or above) and demos (people). It refers to the spread of an infection in a human population in a relatively short period of time. A disease is considered to be an epidemic if the number of new cases is significantly higher than what would normally be expected in the same population. The spread of an epidemic is usually rapid and uncontrolled. The term is used in relation to infectious diseases such as rabies, plague and polio but can also apply to other health conditions like cancer.

Epidemics have powerfully shaped the economic, political and social aspects of human history, driving the development of principles of epidemiology and public health. These outbreaks have given rise to vaccines, antibiotics and antiviral agents.

Pandemic

The World Health Organization defines a pandemic on the basis of a disease’s speed of spread and its geographical reach. A virus is considered to be a pandemic if it rapidly affects many countries and populations with a high incidence of infections and deaths. A flu pandemic is an example of a global pandemic, as are the recent outbreaks of Ebola in West Africa and COVID-19 in the United States. These global pandemics have largely been driven by the fact that a novel coronavirus has no immunity in humans, meaning it can spread incredibly quickly from person to person.