Wondering, pandemic vs. epidemic, what’s the difference? These two terms are often used similarly, even among experts. Both pandemic and epidemic may be used to refer to the rapid spread of an infectious disease; and both terms may be used in reference to the same illness at different points of its development. What is the difference between an epidemic and a pandemic? It’s a matter of scale: a pandemic may affect countries while an epidemic has spread throughout a community or region.

As the western world confronts its first pandemic in over 100 years, the coronavirus, we’re left wondering about the differences between an epidemic vs pandemic, and asking what we can learn from the past. What was the worst one in history? And what can we do differently?

As always, the following is not medical advice. If you have questions about your health or COVID-19, please speak with your physician. Additionally, please see the CDC website for current information on the evolution of the coronavirus.

Pandemic Definition

Typically the definition of a pandemic is an outbreak of an infectious disease that affects a large portion of the population across a large geographic area, usually different countries.

• An illness that spreads quickly (does not have a stable infection rate).
• A disease for which people do not have immunity
• Affects a large population.
• Exists in a large geographical area, typically across countries, continents, or worldwide.

Keep in mind that the severity of a disease does not affect whether or not it is defined as a pandemic.

For example, Ebola, which has a fatality rate of approximately 50% according to the WHO, was considered an epidemic between 2013 and 2016 specific to Western Africa. At the time of writing, there is an Ebola outbreak in the Congo. In neither case is it considered a pandemic.

What Is the Difference Between an Epidemic and a Pandemic?

On March 11, 2020, the World Health Organization (WHO) classified SARS-CoV-2, also known as the coronavirus or COVID-19, as a pandemic. Before that, it was considered an epidemic. So, what’s the difference?

• A pandemic is global. An epidemic is regional.
• Both have high rates of contagion.
• Both describe illnesses for which people do not have immunity.
• Pandemic vs epidemic is decided by the WHO.
• By declaring an outbreak to be global, the WHO is alerting governments to start preparing for community spread, an influx of hospital patients, funding allocations, increased depend for ppe and gear like face shields, and instituting other preventative measures.

The difference comes down to the rate of spread and regions affected. When the virus had officially spread across different countries and infections were consistently and clearly increasing globally, it’s status changed.

Who Decides What Is and Isn’t a Pandemic?

The World Health Organization (WHO) is responsible for making that call. The WHO is an agency within the United Nations responsible for safeguarding global health. 

There are several classifications for a disease determined by the WHO. These classifications determine what health organizations can do to fight a specific disease. It affects things like funding and alerts individuals and governments that an illness is to be taken seriously.

For instance, it tells governments that community spread — contagion without known contact with an infected person — is likely. Additionally, it tells governments to start preparing hospitals for an influx of pandemic-related patients.

WHO Pandemic Definition Phases

A disease cannot be immediately classified as a pandemic. According to the WHO, a disease’s spread may be classified into six phases:

• Phase 1: A new virus is affecting animals but there is no sign of transmission to humans.
• Phase 2: A new virus affecting animals has been transmitted to humans and there is some risk.
• Phase 3: The virus affecting animals has been transmitted to a number of humans but the risk of person to person transmission is low. 
• Phase 4: Community outbreaks are occurring as a virus transmits from human to human. The risk of a pandemic emerging becomes greater. 
• Phase 5: The new virus is transmitting person to person in two countries. At this point the WHO may consider a pandemic unavoidable.
• Phase 6: Another country is affected by the new virus. It is officially a pandemic.

What Is an Endemic vs Epidemic vs Pandemic?

An endemic disease is specific to a region and not spreading at the same rate as an epidemic or a pandemic. An epidemic covers a large region and is considered more out of control. A pandemic is on a global scale.

For example, Hepatitis B (HBV) and malaria may be considered endemic in certain parts of the world.

What Is the Difference Between an Endemic and an Outbreak?

The next step between endemic and epidemic is outbreak. An outbreak may turn into an epidemic if not controlled. It may also refer to the spread of a disease to a region in which it is not endemic.

14 Examples of Epidemics

Coronavirus is far from the first pandemic or epidemic. In many cases, it may be tough to identity the differences between the two because ancient cultures did not use the same language — or have the same preventative measures — as we now do. In many cases, they were referred to as plagues.

Here are a few examples of pandemics throughout history:

1. 430 BCE: The Plague of Athens occurred during the second year of the Peloponnesian War between Athens and Sparta (and other leagues). It is estimated to have claimed as many as 100,000 lives.
2. 165–180: The Antonine Plague affected Romans for years. It is estimated that as much as 10 percent of the Roman Empire’s 75 million people did not recover.
3. 249–262: The Plague of Cyprian spread from Alexandria to other train ports. One account from the bishop of Alexandria estimates that the city’s population dwindled by approximately 62% from death and people fleeing.
4. 1346–1353: The Bubonic Plague, also known as the Black Death, was a pandemic that affected Asia and Europe throughout the mid-1300s. It is estimated that the Bubonic Plague killed almost a third of Europe’s population — 20 million people — over several years.
5. 1545–1548: The Cocoliztli Epidemic affected Central America and North America, and is thought to have killed between 5 and 15 million Mexicans within three years. This represented up to 80% of the population at the time.
6. 1665–1666: The Plague of London was a resurgence of the Black Plague killed up to 100,000 London residents, or 15% of the population.
7. 1889–1890: Influenza viruses, the first of which referred to as the Russian pandemic, spread throughout the world thanks to improved transportation. Even without planes, the pandemic peaked in the United States only 70 days after its peak in St. Petersburg.
8. 1916: The first polio epidemic occurs in the United States. Until a vaccine was developed, polio accounted for 15,000 cases of paralysis annually.
9. 1918–1920: The Spanish Flu killed between 20–40 million people globally — more than World War I. It is thought of as the worst pandemic in modern history.
10. 1981-today: The AIDS Epidemic (sometimes referred to as a pandemic) has killed 32 million people globally since it was discovered. Today, more than 1.1 million people have AIDS.
11. 2002–2004: SARS-CoV (Severe Acute Respiratory Syndrome) was classified as an epidemic, not a pandemic, and resulted in 8,000 cases in 26 countries, concentrated in Asia.
12. 2009–2010: Swine Flu, also called H1N1, was labeled a pandemic — the first in 40 years. At one point 48 of the 50 states had cases simultaneously.
13. 2014–2016: The Ebola Epidemic resulted in the deaths of 11,325 people (28,600 cases) in two years, concentrated in West Africa. In 2020, there is a resurgence of Ebola cases in the Democratic Republic of the Congo.
14. 2019-today: The Coronavirus Pandemic continues to affect virtually every country worldwide. At the time of writing, over 383,000 people have died from COVID-19, over 108,000 in the United States.

What Was the Worst Pandemic In History?

The Black Death is considered one of the worst pandemics in history, having killed 30 million people in approximately 6 years. The Spanish Flu is considered the worst in modern times, resulting in the deaths of between 20–40 million people. Due to the lack of accurate data for many of the world’s epidemics, it is challenged to determine which had the highest death count and rate of infection.

Is Coronavirus a Pandemic?

Yes, the World Health Organization has classified COVID-19 as such, as of March 11, 2020.

Epidemic vs Pandemic: In Review

The coronavirus is officially classified as a pandemic, meaning that it has spread globally and has a high infection rate. It is far from the first of its kind, however: History has been dotted with infectious disease breakouts, some with higher impact than others.

The above information is meant for educational purposes. It is not medical advice.