Pandemic vs. Epidemic: What’s the Difference?

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COVID-19 rapidly spread across the globe in early 2020, and the World Health Organization (WHO) declared the disease a pandemic on March 11. But what is a pandemic? And how is it different from an epidemic?

View the infographic below to learn more, created by Ohio University’s Online Master of Science in Nursing.

How epidemics and pandemics impact health and health care.

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Chapter 1: Pandemic vs. Epidemic

A pandemic starts out as an epidemic and then spreads across countries and continents, infecting people around the globe.

Key Differences

  • An epidemic occurs:
    • In a locality where the disease is not permanently prevalent [Dictionary]
    • When an infectious agent suddenly becomes highly transmissible in an area where it already existed
    • When an outbreak spreads across a previously unaffected area
    • When individuals who were previously immune to an infectious agent suddenly become ill after contracting it
  • A pandemic is an epidemic that has spread across geographic regions. [Healthline]

Key Phases in the Development of a Pandemic

  • A pandemic entails six phases, according to WHO:
    • A virus is transmitted among animals but not humans.
    • The virus is detected in animals capable of infecting
    • An animal infects a human.
    • Humans infect each other and introduce the possibility of a community outbreak.
    • The virus spreads to humans in at least two countries in the same region.
    • A third country, in a different region, experiences community-level outbreaks, indicating a pandemic. [Healthline]

Key Terms

  • Endemic: An infectious disease that is always present in a region
  • Sporadic: When an outbreak occurs in an irregular pattern
  • Outbreak: A spike in the number of cases of an illness in one area beyond what health officials expect [Healthline]
  • Animal-human interface: When humans and animals interact after land is developed for human use but forest animals remain present, leading to the spread of disease
  • Index case: The first person infected with a pathogen — also known as “patient zero”
  • Reservoir: An animal, plant, or environment in which an illness may exist for a prolonged period of time
  • Spillover: The transmission of disease between species
  • Vector: A living being that infects another living being
  • Zoonosis: Any illness that spreads from animals (including insects) to people [Becker’s]

Chapter 2: A Brief History of Epidemics and Pandemics

For thousands of years, infectious diseases have ravaged nations and continents, impacting many areas of life.

The Impact of Epidemics and Pandemics

  • Cholera epidemic (Hamburg), 1892
    • News of the illness was suppressed by merchants, who feared the effect of quarantine on trade.
    • Cholera claimed 10,000 lives in about six weeks.
    • The outbreak was heavily documented in personal letters, diaries, and newspapers. [New Yorker]
  • Spanish flu pandemic, 1918
    • Influenza infected about one-third of the world population.
    • Poor hygiene, increased travel during a world war, and extremely crowded living conditions led to increased virality.
    • The pandemic ended in the summer of 1919. [Healthline 2]
  • Swine flu pandemic, 2009
    • H1N1 infected about 24% of the world population.
    • The disease is treated with antivirals.
    • The pandemic ended in August 2010.
  • Ebola epidemic, 2014-2016
    • The virus is transmitted through bodily fluids, such as sweat and blood.
    • Ebola spread across 10 countries during the epidemic, with 28,652 cases.
    • No vaccine or treatment was available. [Healthline 2]
  • Zika fever epidemic, 2015
    • Zika virus spreads through mosquitoes of the Aedes genus and is sexually transmitted in humans.
    • It attacks infants in the womb and causes birth defects.
    • The virus flourishes in warm and humid climates. [Livescience]
  • COVID-19 pandemic, 2020
    • The novel coronavirus was first detected in Wuhan, China.
    • It’s transmitted through respiratory droplets, feces, and other bodily secretions.
    • COVID-19 is most threatening to adults over 65 with underlying health conditions. [Healthline 2]

The Positive Effect of Scientific Advancements on Infectious Illnesses

  • Prior to the 20th century, scientists didn’t know what caused a disease and believed, for example, that an invisible gas rising from the ground caused cholera.
  • The development of germ theory in the late 19th century showed that bacteria spread
  • The development of the microscope allowed scientists to see microscopic organisms.
  • The discovery of how germs are transmitted led to improved hygienic measures. [New Yorker]

Chapter 3: How Epidemics and Pandemics Impact Health Care

COVID-19 has impacted health care practitioners in different ways, depending on their area of practice and geographical location.

How Health Care Organizations Adjust During the Pandemic

  • During COVID-19, nurses have been:
    • Leading response efforts
    • Overseeing disaster preparedness
    • Managing hospital and field operations
    • Performing predictive modeling
    • Managing human resources [Scientific American]
  • Hospitals across the country pushed to reduce unnecessary visits and increase care provided through telehealth. [Modern Healthcare]
  • According to a survey conducted between April 7 and April 8, 2020, medical practices have experienced the following changes since the crisis began:
    • A 60% drop in patient volume, on average
    • A 55% decrease in revenue, on average
    • Staff furloughs among 48% of practices
    • Permanent staff layoffs among 22% of practices [Fierce Healthcare]

Four Ways COVID-19 May Change Health Care

  • New strategies for elective surgeries.
    • Health care organizations must learn to approach patients who delayed elective surgeries and procedures in ways that make them feel safe.
    • Patients who are unwilling to undergo surgery in a hospital are turning to ambulatory surgery centers for their procedures.
  • Greater development of local supply chain sources.
    • COVID-19 has exposed serious flaws in hospital supply chains for vital equipment, such as respirators and personal protective equipment (PPE).
    • Competing health systems have been forced to work together to obtain equipment and supplies.
  • Acceleration of digital health options.
    • Health care organizations did a decade’s worth of work in a few months to implement telehealth technology.
    • Consumers have realized that they have many virtual and digital health care options to choose from.
  • Innovations with drones and robotics.
    • Disinfection robots can limit how many health care practitioners are exposed during a cleaning
    • The adoption of robotic innovations among health care organizations often follows consumer adoption. [Fierce Healthcare 2]


Every crisis exposes a system’s weaknesses and strengths, forcing organizations to adapt quickly and develop innovative solutions. As a result of COVID-19, the U.S. health care system will likely experience rapid progress and growth spurred by innovations in technology and care delivery.