Outbreaks, Epidemics, and Pandemics

On March 11, 2020, the World Health Organization declared COVID-19, the disease caused by the coronavirus, a pandemic. Prior, the disease was designated an epidemic. What is the difference?

  • Outbreak: a sudden increase in the number of people sick with a disease. Outbreaks last for different lengths of time and can impact a community or a much larger geographic area. For example, every year we anticipate an outbreak of the flu. We can protect ourselves from becoming infected with the flu by using a vaccine. Vaccines reduce the number of people who get sick and result in a smaller, shorter outbreak.
  • Epidemic: an outbreak of disease that spreads quickly and affects many individuals at the same time.
  • Pandemic: an epidemic which spreads over a greater geographic area, often worldwide, and impacts an exceptionally high amount of the population. Pandemics often involve a new virus or a strain of a virus that is not commonly seen. When there is a new virus or a new strain, humans have little to no immunity and the virus can spread easily. Pandemics have social and economic impact in addition to the impact on human health.
  • Has this ever happened before? There have been many pandemics and epidemics throughout history with varying death tolls. The Bubonic or Black Plague, Spanish Flu, HIV/AIDS, and, now, COVID-19. Here is a helpful Infographic to learn more about the history of pandemics and provide some context to this rapidly evolving situation.

Coronavirus v. COVID

  • Coronavirus: coronaviruses are a group of viruses named for the crown like spikes on their surface. There are several types of coronaviruses that can infect people. People around the world are regularly infected by the four known human coronaviruses (229E, NL63, OC43, and HKU1). These viruses cause mild illness, like the common cold. Coronaviruses can infect animals, evolve to infect humans, and become new, or novel, coronaviruses. Three recent examples are:
    • MERS-CoV: a coronavirus that causes Middle East Respiratory Syndrome or MERS)
    • SARS-CoV: a coronavirus that causes severe acute respiratory syndrome or SARS
    • SARS-CoV-2: the new, novel, coronavirus that causes coronavirus disease 2019 or COVID-19
  • COVID-19: the newly identified (or novel) coronavirus causes the disease COVID-19 (COronaVIrus Disease 2019). It is suspected that this virus began infecting animals, changed, then started to infect humans. COVID-19 was initially linked to a live animal market in China but is now spreading from person-to-person throughout the world.

Understanding Transmission of a Virus

During an outbreak, public health specialists work to identify who is sick, their symptoms, when they got sick, and where they might have gotten sick. Every virus spreads, or transmits, differently. By gathering this data and doing a process called contact tracing, public health officials are better able to control the disease. Some viruses are highly contagious, meaning they spread very quickly and easily from one person to another. Measles are an example of a highly contagious virus. Another important difference between viruses is if the virus spreads continually without stopping, which is called a sustained spread.

Contact Tracing

Contact tracing work done by the World Health Organization and local officials in China resulted in the current belief that COVID-19 originated in a live market in China. If you look at reports of COVID-19 cases on the website of your local Department of Public Health or Health and Human Services (we have created a map so you can find your state’s COVID-19 information center) you may see information about transmission or how the virus was acquired.

Public health officials rely on contact tracing to control an outbreak. By knowing where someone has been and who they have been around, public health officials can identify individuals that may have been exposed to the virus by that person and prevent additional people from becoming infected. In the early days of an outbreak, this is much easier because fewer people are infected. As more and more people become infected, contact tracing becomes much more difficult as the numbers rise exponentially.

This information is important for contact tracing.

Types of Transmission

  • Person to Person: the virus is spreading from one person to another. COVID-19 is thought to spread mainly between individuals who are in close contact with one another (within 6 feet) through the respiratory droplets from someone who is infected when they cough or sneeze. If you are standing close enough, you could inhale those droplets into your lungs and become infected as well. You may also see this as close contact. This sort of a case means we have clearly traced an infection to another individual source.
    • Close contact: being within 6 feet of someone for an extended period of time or when they sneeze or cough.
  • Travel: COVID-19 is now in every single state and most countries. However, there are some states with more cases than others. Travel from a location with many cases results in wider spread of the virus. Travel is an important part of contact tracing. Doctors ask patients about recent travel history if they present with symptoms of COVID-19. This can help them decide if the person is at risk for COVID-19. Also, doctors will need to know where that person has traveled in case they were infectious and spread the virus further. For example, in Massachusetts there were no cases on Martha’s Vineyard, a small island off the coast. However, someone from the mainland traveled to the island and now there are confirmed cases on the island. It is really important to limit travel right now because we will also limit the travel of the virus.
  • Community Spread: many states are experiencing community spread. Community spread means that many people in an area are infected and some do not know how or where they were infected. As of this writing, more than half of the states in the US are reporting community spread. This elevates the risk for everyone in the area and makes the spread of the virus much harder to contain. If you are living somewhere there is community spread, you need to be extra cautious. Check out our FAQs to help you navigate!

Presumptive v. Confirmed v. Suspect Cases

  • Presumptive versus Confirmed Cases: testing right now is being done at the state level. When COVID-19 began spreading in the United States, state labs could test someone but were then required to submit the test to the CDC for confirmation. If someone tested positive at a state run lab they were a “presumptive case” and, if the CDC lab confirmed the positive result, that person would then be considered a “confirmed case.” As of March 14, 2020, CDC confirmatory testing was no longer required to consider a positive test done at a state lab confirmed. You may still see presumptive cases listed if a lab that is not run by the state conducted the test; this sample does need to be sent to a state or federal lab for confirmation.
  • Suspect Cases: you may have been heard or read about suspect cases of COVID-19. If someone is showing symptoms of a COVID-19 infection they will be tested for other illness that may cause similar symptoms, like the flu. If they have no other illness that could cause the symptoms and they have had close contact with someone who does have COVID-19 or they live in a country/area where there is community spread happening, they will be considered a suspect case of COVID-19.

Underlying or Preexisting Medical Conditions

Some groups have been told they are at a heightened risk for developing complications if they become infected with this virus. It’s hard to know who falls into this category. We have included, below, the CDC’s current listing of underlying health conditions that may put you at a higher risk. If you are unsure or if you are living with chronic disease not listed below, please be sure to contact your doctor with your concerns. The CDC is currently listing the following people as being at high-risk for severe illness from COVID-19:

  • People aged 65 years and older
  • People who live in a nursing home or long-term care facility
  • People of any age with the following:
    • Chronic Lung Disease: moderate to severe asthma, emphysema, COPD
    • Diabetes Mellitus: Type 1, Type 2, and Gestational (related to pregnancy)
    • Cardiovascular (or heart) Disease
    • Chronic Renal (or kidney) Disease, particularly if not well-controlled
    • Chronic Liver Disease
    • Immunocompromised Condition including but not limited to:
      • Cancer Treatment
      • Bone Marrow or Organ Transplant
      • Immune Deficiencies
      • Poorly controlled HIV or AIDS
      • Prolonged use of corticosteroids (like prednisone) or other immune weakening medications
    • Severe obesity (a BMI of 41 or higher)
    • Pregnancy (people who are pregnant are known to be at risk with severe viral illness)
    • Current or Former Smoker

Social Distancing

Social Distancing for an Individual: making sure there is distance between you and other people to avoid spreading illness. Staying at least 6 feet away from other people reduces your chances of becoming ill with COVID-19.

Social Distancing for a Community: steps taken to reduce large crowds or gatherings; it is hard to maintain distance at a social gathering or in a crowded space. This might include the following:

  • Cancelling or postponing religious/cultural ceremonies like weddings, baptisms, bat/bar mitzvahs, etc.
  • Working from home/remote instead of going to an office
  • Closing schools or switching to online classes
  • Cancelling or postponing large conferences
  • Limiting the number of people allowed to gather in an area
  • Using tele-medicine for doctors’ appointments instead of in-person appointments

Self-Quarantine v. Isolation

Self-Quarantine: someone who has been exposed or who may be sick with COVID-19 might be asked to self-quarantine. This lasts 14 days because two weeks is enough time to know if you will become sick and contagious to other people. After a self-quarantine period has ended, if you don’t have symptoms, follow your doctor’s advice on returning to normal life. If you recently traveled somewhere with a lot of COVID-19 cases or if you have been exposed to an infected person you might be asked to self-quarantine. This involves:

  • Frequent hand washing and standard hygiene
  • Not sharing towels and utensils with others in your household
  • Staying at home
  • No visitors
  • Social distancing from people in your household

Isolation: making sure people who are confirmed to have COVID-10 stay away from those who do not have it. Isolation may happen at home or at a hospital or similar health care setting.

Exponential Spread and Flattening the Curve

A lot of people have been talking about Flattening the Curve and Exponential Spread. But what does all of this really mean for COVID-19? This virus spreads quickly and easily in communities. The number of people sick could become very large, very quickly. Using protective measures, like social distancing, self-quarantine, and isolation, are attempts to keep this from happening, or flattening the curve. The curve (line on the graph) shows the number of people getting sick and needing doctors’ assistance or hospitalization. If too many people get really sick, all at once, in a matter of days, hospitals could become overloaded and the health care system would be overwhelmed. This would also mean more people could die because they may not be able to get the help they need. By flattening the curve, the same number of people may get sick but instead of happening all at once, it happens over time, to make sure people can be taken care of as best as possible.

Here is a great video that describes exponential spread, flattening the curve of COVID-19 infections, and what you can do to help your community.

Last updated on September 11th, 2023 at 12:35 pm

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