An epidemic (from Greek ἐπί epi “upon or above” and δῆμος demos “people”) is the rapid spread of infectious disease to a large number of people in a given population within a short period of time, usually two weeks or less. An epidemic may be restricted to one locale such as a city or country, or may affect populations across continents. Epidemics are often caused by infectious diseases, which may be transmitted through the air, water, or food supply; direct contact with an infected person; or vectors such as mosquitoes, contaminated needles, and syringes.
The term outbreak is sometimes used interchangeably with epidemic, but usually refers to a smaller scale occurrence of similar nature. An outbreak may affect only those at the local level while an epidemic affects larger numbers over a wider area. Outbreaks are often controlled more easily because they are localized and therefore containable. Once an epidemic has begun however, it can be very difficult to control due to its rapid spread among the population.
Epidemics can have devastating effects on communities and economies. The Black Death Plague that swept Europe in the 14th century killed an estimated 30-60% of the European population. More recently, HIV/AIDS has had a profound effect on many countries in Africa where Whole villages have been wiped out as adults die from the disease leaving behind orphans who are unable to care for themselves. The Ebola virus also caused devastation in Liberia, Sierra Leone and Guinea in 2014-2016 with over 28000 people dying from the disease. Epidemics can cause widespread panic and fear as well as lead to social stigma against those affected by it such as happened during the AIDS crisis in North America in the 1980s when there was little understanding about how HIV was transmitted leading to discrimination against sufferers.
It is important for communities to be aware of how epidemics start and how they can be prevented. Good public health infrastructure including access to clean water, sanitation facilities and vaccination programs play a key role in preventing epidemics from occurring or spreading if they do occur. Early detection systems that can identify outbreaks quickly are also essential so that containment measures can be put into place quickly before an epidemic gets out of control