What Is a Pandemic? Definition, Examples, and How It Compares to an Epidemic
Key takeaways:
A pandemic is when a disease affects the global population. Pandemics are usually caused by new infectious agents (bacteria or viruses) that spread quickly.
A pandemic is a type of epidemic, however a pandemic involves the number of people and the geographical area that the disease affects.
Experts suggest that the prevalence of pandemics has gone up as a result of increased global travel and urbanization.
We’ve all been living in a pandemic for quite some time now, but how does it differ from an epidemic? Read on to learn more about the different classifications of disease outbreaks and how they happen.
What is a pandemic?
The Centers for Disease Control and Prevention (CDC) defines a pandemic as a disease outbreak that has spread across multiple countries and continents and usually impacts many people. The classification of “pandemic” comes when a disease affects the global population. Pandemics are usually caused by new infectious agents (bacteria or viruses) that spread quickly.
The WHO has laid out defined phases of an outbreak that progress to the declaration of a pandemic.
| Phase | Description |
|---|---|
| 1 | No animal flu virus has been reported to cause infection in humans. |
| 2 | An animal flu virus in domesticated or wild animals has caused infection in humans and is considered a potential pandemic threat. |
| 3 | An animal or human-animal flu virus has caused clusters of disease in people but has not resulted in human-to-human transmission rates that suggest a community outbreak. |
| 4 | Human-to-human transmission rates are enough to indicate that community outbreaks have been confirmed. |
| 5 | The virus has caused ongoing community outbreaks in two or more countries. |
| 6 | In addition to Phase 5 criteria, the virus has caused community outbreaks in at least one additional country. |
| Post-peak period | Levels of the pandemic have dropped below peak levels. |
| Post-pandemic period | Levels of flu activity have returned to the normal levels seen for seasonal flu in most countries. |
What’s the difference between how a pandemic is defined and how an epidemic is defined?
A pandemic is a type of epidemic. The two differ when it comes to the number of people and the geographical area that they affect.
Epidemic Definition: A disease outbreak specific to one city, region, or country. An epidemic typically starts and spreads quickly. They occur somewhat regularly around the world, but you might not know much about an epidemic unless it is directly impacting your community.
Pandemic Definition: A type of epidemic that has spread worldwide, affecting many countries and continents. Neither the WHO nor the CDC specify exactly how many countries need to be affected for a disease outbreak to be classified as a pandemic. But experts seem to agree that when it comes to pandemics, nearly everyone in the global population is at risk of being exposed.
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How do pandemics occur?
All pandemics start as localized disease outbreaks that then begin spreading rapidly, and eventually around the world. Experts say that the likelihood of pandemics has gone up due to increased global travel and urbanization. As people live in more densely populated areas and are able to more easily travel around the world, disease can spread much more quickly.
In the case of the COVID-19 pandemic, healthcare workers in Wuhan, China started reporting something strange to the WHO office in China in late 2019. They were noticing a cluster of unusual double lung infections with no clear cause.
All the early cases of the COVID-19 could be traced back to one place: the Huanan Seafood Market in Wuhan. This market is known as a “wet market” where live fish, meat, and wild animals are sold. These markets can create an ideal breeding ground for new viruses.
In these markets, many different animal species come into close contact with one another. This makes it easy for viruses to hop from one species to another. As the viruses do this, their genetic code changes and a new strain of animal virus starts. That virus can then infect a human as it comes into contact with a human’s mouth, eyes, nose, or blood when the infected animal is butchered.
This is what happened in Wuhan, China. And because it is a new virus, humans have very little immunity to it. That’s partly why it has become such a big problem. There have been more than 90,000 confirmed cases of COVID-19 in China, and over 244 million cases (and counting) in countries across all continents. This fast spread around the world is what makes this outbreak a pandemic.
Other examples of pandemics in recent history
As the current COVID-19 pandemic unfolds around us, many people are looking back on past pandemic outbreaks for comparison.
The 2009 swine flu pandemic: The flu strain that caused this outbreak, H1N1, was first identified in the U.S. in April 2009. It was characterized by an unusual combination of influenza viruses that had never before been seen in humans, and it began to spread around the globe quickly. On June 11, 2009, the WHO made the announcement that the Swine Flu outbreak had met the definition of a pandemic. By October, the U.S. started administering a vaccine to protect against this unique strain of the virus. The pandemic was considered over by August 2010, and by that time close to 285,000 people around the world had died.
The HIV/AIDS pandemic: The first cases of HIV, the virus that causes AIDS, appeared in 1981. Since then, more than 70 million people have been infected around the world, and nearly 35 million people have died. HIV continues to be a major public health issue as roughly 38 million people were still living with the virus at the end of 2018. It is still, nearly 40 years after the first cases, a leading cause of death globally. However, deaths have declined over time as new treatments have become available.
The 1918 Spanish flu pandemic: The 1918 Spanish influenza outbreak is still said to be one of the worst pandemics in recent history. This meets the definition of a pandemic as roughly one-third of the world’s population was infected with this flu virus. The global death toll was estimated at more than 50 million people, with about 675,000 deaths in the U.S. The first cases were reported in Kansas, and as hundreds of thousands of U.S. troops were deployed during World War I, the virus began to spread.
The bottom line
A pandemic is a specific type of epidemic, affecting various geographical regions. There have been numerous outbreaks throughout time, with the coronavirus disease being the most prevalent at this time. You can stay up to date on the latest COVID-19 mandates and vaccine approvals with our live trackers.
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