As discussed in a previous post, using the right words is crucial when writing about infection and infectious diseases.
Disease occurrence has been gaining global attention in recent years, so today’s focus is on key terms related to frequency and geographic distribution in the field of epidemiology, the science that studies how diseases, including infectious diseases, spread within populations.
Endemic refers to a disease that typically occurs in a specific population or geographic area at regular frequency. So, for example, we know that malaria is endemic in many regions of Africa because people regularly contract it from the bites of the mosquitoes that live in those areas. Another example of endemic is the seasonal flu.
Sporadic is used when only a few scattered cases of a disease occur within a population or area. These cases are usually fewer than those observed for endemics and are separated in space and time. Also, the sources and connections between those cases are usually unknown.
Epidemic is used to indicate sudden or unexpected increases in disease occurrence in a given population or area. The connection between cases and source is usually known. Examples of diseases that cause epidemics are measles and yellow fever.
Pandemic refers to widespread disease occurrences that involve multiple countries and continents and affect many people. Examples of diseases that have caused pandemics include AIDS and COVID-19.
For disease occurrences to be categorized as endemic, sporadic, epidemic, and pandemic, health agencies and departments must record cases for individual regions and populations, carefully noting any changes in data.
The terms described above only refer to disease spread and distribution and not disease severity.
Also, while we tend to think of these terms being related to viruses or other pathogens, the occurrences aren’t always infectious in nature. For example, obesity is considered an epidemic.
Want to learn more?
Read informative content on the WHO website.
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Search our blog posts on Word Usage.
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