Something is endemic if it is found in a particular geographic area, population or region. An endemic disease is constantly present in a particular area: for example, AIDS is endemic in parts of Africa. When used to describe a species, however, endemic refers to being native to a specific location and found naturally nowhere else.
The words pandemic, epidemic and endemic often come to public attention in relation to infectious diseases. They share a common root from the Ancient Greek word demos (people), but have distinct meanings. This can be seen clearly in relation to the rise and spread of covid-19.
In late 2019, the disease emerged in Wuhan, China. At first, it was an epidemic, a sudden outbreak that spread rapidly among the people in that city. Despite strict quarantine measures, public health officials were unable to contain the virus, SARS-CoV-2. In March 2020, the World Health Organization declared it to be a pandemic, meaning that it had spread widely around the world.
A year later, the covid-19 pandemic was still raging. However, in early 2021, almost 90 per cent of researchers surveyed predicted that it would become endemic over time. In other words, they believe it won’t be completely eradicated but instead will have a constant presence among particular populations in various parts of the world. If so, then, like other endemic diseases, covid-19 may flare up from time to time, resulting in local epidemics.
One reason so many experts think that SARS-CoV-2 will become endemic is that this is what has happened to four other coronaviruses that infect humans. When people first became susceptible to them, they seem to have triggered epidemics or pandemics, but now, a few centuries later, they are endemic in most countries, and have become no more serious than a common cold.
A disease can be described as pandemic or epidemic, but these words can also be used as nouns: a disease can be a pandemic or an epidemic. The word endemic, by contrast, is rarely used as a noun. There is one exception. Biologists do sometimes refer to a species that is confined to a single defined location as “an endemic”. For example, lemurs are found only on the island of Madagascar, making the 100 plus species “endemics”. Nevertheless, you are probably more likely to hear them described as endemic species.