When the number of disease cases rises above what’s typically expected in a specific area, it’s called an epidemic. This usually happens suddenly and often involves a large number of people. In the past, smallpox, cholera, yellow fever, and typhoid were all considered epidemics. Today, HIV and drug-resistant tuberculosis are among the diseases classified as epidemics.
The word epidemic comes from the Greek words epi, meaning upon or above and demos, meaning people, which suggests that a disease spreads rapidly across a population. The term is also used to describe other health risks, such as the rapid increase in the percentage of people worldwide who are obese (often referred to as an obesity epidemic).
Infectious disease outbreaks can cause great disruption and anxiety for people around the world. The fear, ostracism and stigma that can accompany an epidemic can linger long after the disease is gone. Resilience-building interventions that help people learn to cope with these negative mental health impacts of outbreaks can be useful.
On March 11, 2020, the World Health Organization declared that the COVID-19 pandemic was international in scope and that its growth rate had exceeded what would be expected for a specific region. The distinction between an epidemic and a pandemic doesn’t have anything to do with the virology of the virus or with a country or region’s level of immunity or disease prevalence. It’s all about the pace of growth.