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Business, Numbers, STEM

Differentiating Between an Outbreak, Epidemic, or Pandemic

Handwashing (Source: WHO)

Handwashing (Source: WHO)

It’s almost Thanksgiving and today is an extremely high travel day for many of us in the United States. As I type this post, my sister is flying to New York to spend Thanksgiving with family and friends. In an earlier post, NUMBERS: Ebola Virus Disease (EVD), I proposed a follow up discussion to differential an outbreak from an epidemic or a pandemic as it relates to infectious diseases. This post will explore these differences as most of you prepare to eat lots of turkey, and as we move further into the flu season.

Since the first case of EVD was reported in the U.S. on September 30th of this year, two persons have died from the disease. Six others either contracted the disease in the U.S. or were diagnosed with the disease after returning from an international trip. Each has been treated and declared ebola-free.

According to the Centers for Disease Control (CDC) and other sources, when a disease occurs in greater numbers than expected in a community or region or during a season, this is known as a disease outbreak. An outbreak can occur in just one community, or can extend to several countries. It can last from days to years.

Sometimes a single case of a contagious disease is considered an outbreak. This may be true if the disease is unknown, new to a community, or has been absent from a population for a long time. Here in the U.S., some referred to the less than two handful of cases that were diagnosed in this country on or after September 30th as an ebola outbreak, while other health professionals were hesitant to do so.

What are the numbers behind a disease outbreak? First it depends on the disease in question. In the case of the flu, the difference between an outbreak and an epidemic is the percentage of overall deaths caused by the disease. Every week, the Centers for Disease Control (CDC) gathers morbidity data from hospitals in 122 cities across the U.S. and calculates the percentage of the decedents that have expired from pneumonia, cancer, and other diseases that they track. If the number of flu-caused deaths exceeds 7.7 percent of the total, then the United States officially has an epidemic on its hands. Again, the percentages for mortality is different for each disease, therefore, the 7.7% does not apply to other diseases such as AIDs, other sexually transmitted diseases (STD), meningitis, a food borne illness such as listeriosis, or EVD.

Unlike other diseases, flu follows an annual pattern each year. Flu season typically stats in the fall of the year here in the U.S., and peaks in January or February. Therefore, as you prepare your Thanksgiving meals, and prepare for Black Friday shopping trips, wash your hands often, cover your mouth when you cough, and avoid rubbing your face or eyes with your hands. Do not underestimate the impact of good hygiene practices in combatting the common cold to highly infectious diseases.

An epidemic occurs when an infectious disease spreads rapidly to many people. In 2003, the severe acute respiratory syndrome (SARS) epidemic took the lives of nearly 800 people worldwide. The CDC’s official definition of an epidemic is “The occurrence of more cases of disease than expected in a given area or among a specific group of people over a particular period of time.”

Since some diseases become more prevalent or lethal over time, while others become less severe, the CDC adjusts its statistical models to alter their definition of truly more than expected. As an example, during the flu epidemic of 1990, the CDC’s threshold was 6.7 percent of total deaths. Today’s threshold figure is likely due in part to the emergence of new, less treatable flu strains, as well as the decline in morbidity associated with other diseases.

More often than not, the terms outbreak and epidemic are used interchangeably. According to CDC, “epidemic” is often preferable merely because it’s a less frightening term.

Words like outbreaks and epidemics should get the attention of every American, however, freaking out about the use of these words is not an option. Knowledge and education of any potential public health issue is of utmost importance! On the other hand, a pandemic is a global disease outbreak that should be top of mind for everyone! HIV/AIDS is an example of one of the most destructive global pandemic in history.

An influenza pandemic occurs when:

  • A new subtype of virus arises. This means humans have little or no immunity to it. Everyone is at risk.
  • The virus spreads easily from person to person, such as through sneezing or coughing.
  • The virus begins to cause serious illness worldwide. With past flu pandemics, the virus reached all parts of the globe within six to nine months. With the speed of air travel today, public health experts believe an influenza pandemic could spread much more quickly. A pandemic can occur in waves. And all parts of the world may not be affected at the same time.

Reasons to give thanks: As I put the finishing touches on this post, I am watching the Today Show. Some of this morning’s guests include six American survivors of EVD. As host Matt Lauer described them, “they are members of a club that they did not want to join”. What they proved to many of us is that one can survive a deadly infectious disease!

Now, what does all of the above have to do with business and STEM? What the six EVD survivors also proved, which may not be as obvious to everyone, is how important good health and a healthy population is to a nation’s security! An epidemic of any disease can weaken any country’s security risk, reduce its ability to produce goods and services, or protect its borders. Healthy communities and populations are  just as important, if not more important than natural resources, energy infrastructure, educated adults, or gross domestic product (GDP).



About Vi Brown

Vi is principal and CEO of Prophecy Consulting Group, LLC, an Arizona firm that provides business and engineering services to private and public clients. Prior to establishing her consulting practice in 2001, Vi worked with Motorola, Maricopa County Government, Pacific Gas & Electric, CH2M Hill, and Procter & Gamble. As an adjunct faculty member, Vi teaches undergraduate calculus classes and graduate level environmental courses. She is also a professional speaker.



  1. Pingback: The Zika Virus: Is a Pandemic Brewing? | BridgeBizSTEM - January 29, 2016

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