Home Others Epidemic, endemic, pandemic: what are the differences?

Epidemic, endemic, pandemic: what are the differences?

Public Health Education, Global Health, Infectious DiseasesFebruary 19, 2021

The novel coronavirus pandemic is the perfect model for understanding what exactly a pandemic is and how it affects life on a global scale. Since the advent of COVID-19 in 2020, the public has been bombarded with a new language for understanding the virus and the global public health response that has followed. This article will uncover the factors that make up a pandemic and how it differs from epidemics and endemics.

What is an epidemic?

The Centers for Disease Control and Prevention (CDC) describes an epidemic as an unexpected increase in the number of illnesses in a given geographic area. Yellow fever, smallpox, measles, and polio are prime examples of epidemics that have occurred throughout American history.

In particular, an epidemic does not have to be contagious. West Nile fever and the rapid rise in obesity are also considered epidemics.

In a broader sense, epidemics can refer to a disease or other specific health-related behavior (e.g. smoking) at rates well above the expected occurrence in a community or region.

What is a pandemic?

The World Health Organization (WHO) declares a pandemic when the growth of a disease is exponential. This means the growth rate is skyrocketing and cases are growing more every day than the day before.

Because the virus is being declared a pandemic, it has nothing to do with virology, population immunity, or the severity of the disease. This means that a virus can cover a wide area and affect multiple countries and populations.

What is an endemic?

A endemic is an outbreak of disease that is constant but limited to a specific region. This makes the spread and rates of the disease predictable.

Malaria , for example, is considered endemic in certain countries and regions.

What are the differences between pandemics and epidemics?

The WHO defines pandemics, epidemics and endemics based on the rate at which a disease spreads. So the difference between an epidemic and a pandemic is not in the severity of the disease, but in the extent to which it has spread.

A pandemic crosses international borders, unlike regional epidemics. This large geographic reach results in pandemics leading to large-scale social disruption, economic loss, and general hardship.

It is important to note that once an epidemic has been declared, it can turn into pandemic status. While an epidemic is large, it is generally also expected to be contained or expected to spread, while a pandemic is international and out of control.

Causes of Disease Outbreaks

Several factors contribute to infectious disease outbreaks. Contraction can occur as a result of transmission from humans, animals, or even the environment. For example:

Causes of disease can also be unknown. These types of diseases can be caused by a variety of factors, including:

  • A new or newly modified pathogen
  • Natural toxins
  • Unrecognized chemical release
  • Unknown overexposure to ionizing radiation

The field of epidemiology is working to trace these unidentified outbreaks back to the source in order to protect public health and safety.

Notable past pandemics

The current COVID-19 outbreak isn't the only disease that has affected the world worldwide. Here are just a few examples of past pandemics that have shaped the evolution of outbreaks and human immunity.

The Black Death (1346-1353): The Black Death caused an estimated 25 million people around the world in the 14th century. According to scientists, the outbreak was caused by a bacterium called Yersinia pestis. The virus lasted for about four years.

American Plagues (16th Century): TOAccumulation of Eurasian diseases brought to America by European explorers, smallpox was one of the major diseases of the American plague that contributed to the collapse of the Inca and Aztec civilizations. Some estimates suggest that 90% of the indigenous population in the western hemisphere were killed as a result.

The flu pandemic (1889 - 1890): New transport routes made possible in the industrial age facilitated the widespread spread of influenza viruses in the United States and beyond. Over the course of months, the flu spread around the globe, with the earliest cases reported in Russia. The virus quickly spread across St. Petersburg before quickly making its way through Europe and the rest of the world, despite no air travel as yet.leaves 1 million people behind.
Spanish flu (1918-1920): Another massive outbreak was the pandemic flu, popularly known as the Spanish flu. This virus pandemic began in 1918, immediately after World War I. Over 50 million deaths were recorded during this outbreak, with the disease lasting only two years.

The Asian flu (1957-1958): The Asian flu pandemic, a mixture of bird flu viruses, started in China and eventually claimed more than 1 million lives. The CDC notes that the rapidly spreading disease was reported in Singapore in February 1957, in Hong Kong in April 1957, and in coastal cities of the United States in the summer of 1957. The total death toll was more than 1.1 million worldwide, with 116,000 deaths in the United States.

AIDS Pandemic and Epidemic (1981 - Present): Since it was first identified, AIDS has claimed an estimated 35 million lives. Scientists believe that HIV, the virus that causes AIDS, likely emerged from a virus found in chimpanzees and transmitted to humans in West Africa in the 1920s. At the end of the 20th century, the virus had found its way around the world.For decades the disease was incurable, but drugs developed in the 1990s now allow people with the disease to lead normal lives with regular treatment.

Learn More: The Columbia School of Public Health has led on every aspect of the global response to HIV, from research into mother-to-child transmission to strengthening treatment and care systems, to the history of stigma, advocacy and education of coalitions.

The way out

A common characteristic of epidemics and pandemics is the need to avoid infection. There is typically a large time lag between an outbreak and the distribution of vaccinations, as we saw with COVID-19. In the meantime, it is important to take the following steps to stay healthy:

  • Wash your hands frequently with soap and water. Use hand sanitizer.
  • Do not touch your mouth or nose without disinfecting or washing your hands.
  • If you cough or sneeze, cover your mouth and nose with a tissue.
  • Avoid crowded places. Stay home if you can.
  • Disinfect household surfaces regularly.
  • Practice social distancing when you leave the house.
  • Outside of your household, use properly fitted face masks and other protective shields.


Since 1922, Columbia Mailman School of Public Health has directed responsibility for research, education, and community collaboration in public health. We address today's pressing public health issues and put the research into action. Find out more about our public health courses.

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