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Updated on June 6, 2025
While the COVID-19 pandemic has transitioned from a global health emergency into a more stable (but still ongoing) issue of public health concern, it remains important to stay up to date on what is happening—and to stay up to date, it helps to have a good idea of the basics.
Essential terms related to COVID-19 infections
Coronavirus
Coronaviruses are a family of viruses named for their crown-like spikes that can be seen when these viruses are examined under a microscope. Some coronaviruses, like 229E, cause the common cold. SARS-CoV-2 is the specific coronavirus responsible for COVID-19.
COVID-19
Short for coronavirus disease 19, COVID-19 is caused by the SARS-CoV-2 virus. While the global health emergency phase has ended, COVID-19 continues to affect many people, and can pose serious health risks to babies under 6 months, older adults, and people with certain underlying medical conditions.
Spike protein
A spike protein (also called an S protein) is a protrusion (like a spike) on the surface of a virus. This protrusion helps the virus attach itself to a cell. Once the virus is attached to healthy cells via the spike protein, it begins to infect the cell. COVID-19 vaccines work by training the immune system to make antibodies that target the spike protein. These antibodies are proteins that attach to the virus and help the immune system neutralize it.
Pandemic
A pandemic is an outbreak of a disease that spreads across countries and continents and causes large and increasing numbers of infections. COVID-19 began as a local outbreak in late 2019 and became a global pandemic in early 2020. Although we are no longer in the emergency phase of the pandemic, COVID-19 remains a public health concern.
Endemic
A disease is considered endemic when it becomes a regular presence in a population, with predictable and manageable numbers of cases. Many experts now view COVID-19 as an endemic illness that will continue to circulate alongside other respiratory viruses, like the flu and RSV.
Variant
A variant is a version of the virus with genetic changes. Some variants, like Delta and Omicron, led to major waves of illness. Today, public health agencies monitor for new SARS-CoV-2 variants that might affect how the virus spreads or how it responds to vaccines.
Mutation
A mutation is a change in the genetic makeup of a virus. These changes can affect things like how easily a virus spreads and how likely it is to infect people with previous immunity, but not all mutations have a significant disease impact.
PCR test
A polymerase chain reaction (PCR) test looks for the virus’s genetic material. This type of test is considered highly accurate. PCR tests for COVID-19 use a nasal swab and are typically administered at healthcare settings, such as pharmacies or healthcare providers’ offices.
Antigen test
This type of test detects proteins from the SARS-CoV-2 virus and determines whether or not you have an active infection. It is typically performed using nasal and/or throat swabs and can be administered at home. These are slightly less sensitive than PCR tests but are easy to use and produce a result in 15 to 30 minutes.
Long COVID
Long COVID refers to a chronic health condition that persists for weeks, months, or years after a COVID-19 infection. These symptoms can include fatigue, brain fog, and shortness of breath (and 200 other potential symptoms). Long COVID may also contribute to or worsen other health conditions, including diabetes, heart conditions, blood clots, and neurological conditions. In some cases, long COVID is severe enough to cause disability.
Wastewater surveillance
This is the practice of testing wastewater (sewage) within a specific geographic area to look for pieces of COVID-19 virus. This has become an important tool for detecting increasing cases of COVID-19 infections. In addition to COVID-19, there is also wastewater surveillance for the flu, avian flu (bird flu), RSV, and Mpox (monkey pox).
Your best source of information
While knowing these terms can help you better understand COVID-19, when it comes to decisions about your health, your best source of information will be a healthcare provider. If you have concerns about how to protect yourself or your loved ones from illnesses like COVID-19, the flu, RSV, or others, make an appointment with your healthcare provider.
