COVID-19: Key Terms to Understand Infection and Spread

A list of key terms and phrases that are essential to understanding the COVID-19 pandemic.

During the COVID-19 pandemic, people have been confronted with a constant update of news, information, and terms and phrases they may be unfamiliar with.

When dealing with any illness, it helps to understand the key terms and phrases that surround that illness. This has been particularly important during the COVID-19 pandemic, where people have been confronted with a constant update of news, information, and terms and phrases they may be unfamiliar with.

With that in mind, the below is a list of key terms and phrases that are essential to understanding the COVID-19 pandemic.

  • Coronavirus. A coronavirus is a virus that looks like it has crown-like spikes on the surface when it’s viewed under a microscope. There are many different types of coronaviruses, including 229E (which causes the common cold) and SARS-CoV-2 (which causes COVID-19).
  • COVID-19. This is an abbreviation for the particular corona (co) virus (vi) disease (d) that was first identified in 2019 (19). Thus, it became known as COVID-19. The term is used to refer to the disease caused by infection with this particular coronavirus.
  • Spike protein. A spike protein (also called an S protein) is a protrusion (like a spike) on the surface of a virus that helps the virus attach itself to a cell. Once the virus is attached to healthy cells via the spike protein it begins attacking. Because the spike protein is the link between the virus and the healthy cells, a lot of vaccine and antiviral research is focusing on how to target the spike protein in order to prevent or stop infection.
  • Pandemic. While an epidemic is an outbreak of a disease over a large geographical area, a pandemic is an outbreak that stretches across the globe. COVID-19 began in one country and quickly spread across the world, becoming a pandemic.
  • Endemic. Endemic is the presence of a disease that is consistent, stable, and predictable, which means it will not end, but people will gain immunity through vaccinations and natural infections. Many experts believe COVID-19 will become endemic.
  • Variant. A variant occurs when there is one or more changes to the genetic makeup of a virus. Two examples include the Delta variant and the Omicron variant.
  • Mutation. A mutation is a change in the genetic makeup of a virus. These changes occur frequently but don’t always change how the virus presents itself.
  • PCR test. A polymerase chain reaction (PCR) test is done to find a specific organism such as a virus. A COVID-19 PCR test looks for the genetic material of the SARS-CoV-2 virus that causes COVID-19.
  • Antigen test. This test looks for molecules on the surface of the virus and determines whether or not you have an active infection. It is typically done through a nasal, throat, or saliva swab.
  • Asymptomatic. Asymptomatic means you have an infection but show no symptoms. If you are asymptomatic, you can still infect others.
  • Positivity rate. This is the percentage of all tests that are positive for the virus.

While knowing these terms can be helpful, your best source of information will be a healthcare provider. If you have concerns about your health or getting vaccinated against COVID-19, talk to a healthcare provider.

Article sources open article sources

Jennifer Huizen. "Why is it called coronavirus?" MedicalNewsToday. September 28, 2020.
Thomas Jefferson University. "Coronavirus Information & FAQs."
NCI Dictionaries. "COVID-19."
Dara Grennan. "What is a Pandemic?" JAMA, 2019. Vol. 321, No. 9.
Centers for Disease Control and Prevention. "Identifying the source of the outbreak."
Harvard T.H. Chan School of Public Health. "What will it be like when COVID-19 becomes endemic?"
Johns Hopkins Medicine. "COVID Variants: What You Should Know."
Centers for Disease Control and Prevention. "SARS-CoV-2 Variant Classifications and Definitions."
Cleveland Clinic. "COVID-19 and PCR Testing."
U.S. Food & Drug Administration. "COVID-19 Test Basics."
Hana Ames. "What does asymptomatic COVID-19 mean?" MedicalNewsToday. September 28, 2021.
Theresa Waldrop. "Coronavirus positivity rate: What the term means." CNN Health. July 7, 2020.
Centers for Disease Control and Prevention. "MERS-CoV Photos."
Johns Hopkins Medicine. "What Is Coronavirus?"
World Health Organization. "Naming the coronavirus disease (COVID-19) and the virus that causes it."
SinoBiological. "Spike Protein / S Protein."
Claire Felter. "When Will COVID-19 Become Endemic?" Council on Foreign Relations. February 18, 2022.
Johns Hopkins Bloomberg School of Public Health. "COVID-19 Testing: Understanding the “Percent Positive."

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