The Difference Between Pandemic, Epidemic And Endemic

A lot of words we’re not used to seeing have popped up in recent months as the coronavirus outbreak worsens globally. Three of those words include pandemic, epidemic and endemic and while some of us likely think they have similar meanings, the words in fact represent distinct stages of a disease’s prevalence. Here’s what they mean.

What is a pandemic?

Starting off with the most serious of terms, a pandemic is loosely defined by the World Health Organisation as the “worldwide spread of a new disease”. In layman’s terms, it means the whole world is affected, not just an outbreak in a country or two.

The 2019/20 coronavirus, or COVID-19, outbreak was classed as a pandemic by WHO on 12 March due to its high prevalence globally.

“Describing the situation as a pandemic requires countries to accelerate their efforts, striking the right balance between protecting health, preventing economic and social disruption, and respecting human rights. I appreciate that this means governmental authorities often face difficult decisions,” WHO’s Regional Director for Europe, Dr Hans Kluge said in a statement.

It initially refrained from calling it that due to the social implications it may cause, such as mass panic, and that a country’s response to the virus doesn’t necessarily change because of its classification.

Other examples of historic pandemics include viral outbreaks such as the 2009 H1N1 or swine flu pandemic, the 1918 Spanish flu outbreak as well as bacterial ones like the infamous Black Death or bubonic plague of the 14th century.

What is an epidemic?

As opposed to a pandemic, an epidemic is a major outbreak contained within a country or a few. Initially, coronavirus was considered an epidemic with pandemic potential when it was first observed in mainland China.

Specifically though, WHO defines it as:

The occurrence in a community or region of cases of an illness, specific health-related behaviour, or other health-related events clearly in excess of normal expectancy. The community or region and the period in which the cases occur are specified precisely. The number of cases indicating the presence of an epidemic varies according to the agent, size, and type of population exposed, previous experience or lack of exposure to the disease, and time and place of occurrence.

Breaking that down, it means a new contagious disease has spread to levels considered more than the normal threshold. That threshold will vary from country to country but serves as an important marker for countries to know when to “step-up appropriate control measures”.

Examples of some epidemics include the 2014 and 2018 Ebola outbreaks, which while very serious, were contained mostly within eastern Africa.

What is endemic?

Endemic is a term you’re likely to hear less often given it is best described as the expected rate of disease prevalent in a country.

As the US’s Centres for Disease Control and Prevention (CDC) explains, the level “is not necessarily the desired level, which may in fact be zero, but rather is the observed level”.

There is also a term sometimes used called hyperendemic, which the CDC says refers to “persistent, high levels of disease occurrence” within a specific area.

Examples of diseases that are usually defined as endemic include melioidosis, a bacteria-caused pneumonia considered endemic in Northern Australia, as well as chickenpox across the entire country.

Do the terms really matter?

At the end of the day, a disease’s classification as endemic, epidemic or pandemic won’t change the response too much but can be an important communication tool to quickly convey the severity of a disease’s outbreak.

For some of us, this won’t make a difference but in tense times when many of us struggle to get a grasp of what’s happening, learning simple things like this can make us feel more in control of our knowledge. That’s all we can really ask for right now.

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