The difference between a pandemic and an epidemic

Some words are interchangeable, depending on context. However, when it comes to “pandemic,” “epidemic,” and “outbreak,” they are far from being the same. Rather, they are indications of how far an illness, virus, or disease has spread. 

Here’s what all those terms mean.

A pandemic

Indicative of mass spread, pandemics are instances in which new diseases that people do not have immunity for “exceeds expectations,” by spreading globally. Past pandemics have included the 1918 H1N1 Influenza (aka as the Spanish Flu)  and 2009 H1N1 (aka as the Swine Flu). Pandemics are determined not only by how far the disease spreads, but also by how difficult it is to contain. For this reason, the 2003 SARS coronavirus was not determined to be a pandemic.

An epidemic

Similar to a pandemic, epidemics are instances of widespread illnesses which do not make it around the world. For example, the SARS coronavirus of 2003 was an epidemic because while it spread to 26 countries, it was “quickly contained,” according to the Guardian. There are four different types of epidemic patterns as described by the CDC, which is made unique by the way people are infected and the disease spreads. 

An outbreak

Often the first step to an epidemic or pandemic before an illness becomes widespread, outbreaks are small clusters of cases which are localized. The same illness can have multiple outbreaks in different countries and regions, remaining large-scale without overwhelming healthcare facilities. Yearly diseases, such as seasonal flu, as well as single cases of extremely rare diseases, can be considered outbreaks. 

Sources: The Guardian, APIC, CDC, CDC on Past Pandemics, WHO

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