For many of us, the year 2020 might have been the first time we were introduced to epidemiological terms such as “pandemic”, “epidemic”, and even “endemic”, as Covid-19 began to spread its devastating effect around the world.

You may vaguely understand that these terms refer to infectious illnesses, but what do they really mean and what differentiates these terms?

Key terms defined

“Pandemics”, “epidemics” and “endemic diseases” are defined by the World Health Organization (WHO) based on the rate of disease spread.

What makes an epidemic and a pandemic different is not the severity of the disease, but the scale of its spread.

Hence, a pandemic is not necessarily worse than an epidemic or an endemic disease.

Pandemics do have the largest potential to cause worldwide disruption, but this depends on the specific disease and how we manage it collectively.

Here are the definitions of these terms:

An endemic disease is consistently present in a specific region or population with a fairly stable prevalence or frequency.

This makes the spread of the disease predictable.

For example, malaria is endemic to some parts of Africa due to the continent’s higher average temperature, while dengue fever is endemic to tropical and subtropical regions like Malaysia.

Another example is hepatitis B, which is endemic worldwide, with higher endemicity in Africa and Asia.

An epidemic is a sudden and rapid increase in the number of disease cases above what is normally expected in a specific region or population.

It can happen when a new disease appears in the population or when an endemic disease becomes more prevalent or widespread.

An epidemic disease is not necessarily contagious and may refer to other diseases or health issues with a prevalence higher than the projected occurrence in a population.

Examples include the Zika virus epidemic in Brazil (2015-2016), the Ebola virus epidemic in West Africa (2014-2016), and the ongoing opioid epidemic in the United States due to the increasing use of opioids and overdose cases in the past decades.

A pandemic happens when a disease spreads across multiple countries or continents, impacting a large number of people.

A disease may be declared as a pandemic if it spreads at a very fast rate, with more new cases reported every day.

An ongoing epidemic may turn into a pandemic if it spreads beyond the originating region or population.

Properties of the pathogen, population immunity or severity of the disease are not factors in determining whether or not a disease is a pandemic.

Examples include the Covid-19 pandemic caused by the SARS-CoV-2 virus (2020-2022), and the swine flu (2009) and 1918 influenza pandemics (also known as the Spanish flu pandemic, 1918-1920), both caused by the H1N1 influenza virus.

Other important terms

There are also other terms that may be used to describe the spread of disease in a population, such as:

This is when a disease happens rarely or occasionally.

Examples include tetanus, which tends to happen only in unvaccinated individuals, or foodborne illnesses such salmonella or Escherichia coli (E. coli) infections.

This is when there is a persistent presence of a disease at a higher level in a population compared to other populations.

For example, in parts of Africa, as many as one in five adults has HIV (human immunodeficiency virus), hence the disease is considered hyperendemic in those places.

This is when a disease occurs at a higher rate in a specific geographical area or time period, but the exact cause may be uncertain.

For example, a cluster of cancer cases that arises after a chemical contamination event or a nuclear plant accident.

This has the same meaning as an epidemic, but is typically used to describe a disease spread that is more limited geographically.

Is Covid-19 endemic?

This is a question that has been asked many times since the world started reopening after the Covid-19 pandemic.

To answer this, we need to understand what it means for Covid-19 to be endemic.

For Covid-19 to be considered endemic, its continued presence in the population must be at a certain predictable level or trend.

The closest example is influenza, which is typically present at an expected level throughout the year in Malaysia.

Yet, being endemic is not necessarily a good thing as the disease can still have severe effects on patients.

Plus, it is possible for an endemic disease to turn into a pandemic again.

Covid-19 is no longer categorised as a pandemic and was officially considered as having become endemic in Malaysia on May 1 (2025) after a three-year transition period that began on April 1, 2022.

Regardless, continued surveillance and vigilance are necessary to prevent another pandemic from happening.

Other than practising ­personal hygiene, taking Covid-19 vaccine booster doses is also part of the preventive measures recommended to everyone, especially high-risk groups such as the elderly and people with underlying medical conditions or weakened immune systems.

Whether it’s endemic or an epidemic or pandemic, let’s continue to prioritise our health and safety!

Datuk Dr Musa Mohd Nordin is a consultant paediatrician and neonatologist, and Dr Husna Musa is a paediatrician. This article is courtesy of the Malaysian Paediatric Association’s Positive Parenting programme in collaboration with expert partners. For further information, please email starhealth@thestar.com.my. The information provided is for educational and communication purposes only, and it should not be construed as personal medical advice. Information published in this article is not intended to replace, supplant or augment a consultation with a health professional regarding the reader’s own medical care. The Star does not give any warranty on accuracy, completeness, functionality, usefulness or other assurances as to the content appearing in this column. The Star disclaims all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.