COVID-19 Resources

Alpha, Beta, Gamma, Delta, Omicron: COVID-19 Variants Explained

Jan. 13, 2023

The COVID-19 pandemic has proven to be nothing if not resilient.

Cases rise, counties sound the alert and precautions are again recommended–it’s a cycle that has become a fact of everyday life, and with that cycle comes a new vocabulary to help us keep track and make sense of our new normal.

Alpha, Beta, Gamma, Delta, Omicron—variants, lineages, mutations; these medical terms have become common in daily life, but they’re confusing for almost anyone. To muddy the waters even further, each variant comes with its own set of symptoms—some come complete with that telltale loss of smell and taste while others don’t. Some variants present with allergy-like symptoms such as a scratchy throat, nasal congestion and cough, while others bring headaches and deep fatigue.

We may think of COVID-19 as one illness, so how do we make sense of all the new variants? How do they evolve? What do we need to know about them? As the variants of COVID-19 continue to form and spread, stay informed as we take an in-depth look at all things coronavirus.


“Some RNA viruses like COVID-19 are unstable,” Jennifer Wall Forrester, MD, said. “That means its genetic code changes just a little every time it infects a new person and replicates within their cells. Those small changes are called mutations. One of the advantages we’ve had during this pandemic is scientists’ ability to map and share the virus’ genetic sequences from patients all over the world. We’ve literally watched COVID-19 evolve in real time.”

The Centers for Disease Control (CDC) defines a mutation as a single change in a virus’ genome or genetic code. While mutations happen frequently, they typically aren’t noticeable. But occasionally, a mutation occurs that gives the virus a new advantage; perhaps it makes the virus spread more easily, or better at evading the host’s immune system.

When one of these mutations occurs, a new variant is created. The World Health Organization (WHO) came up with the idea of naming variants after the Greek alphabet to make it easier for the public to keep track. On Nov. 30, 2021, the U.S. government classified Omicron as a new variant because this variant was rising in many countries, and because scientists determined the virus cells now had yet another new look and behaviors.

What are Virus Variants?

Think of a tree, with its broad trunk that spreads into smaller branches—now think of the trunk as COVID-19, and the branches as its variants. Since the start of the pandemic, scientists have been comparing the branches and cataloging them based on those slight differences.

The Beta variant was a little different from the original COVID-19, which is now called the Alpha variant, and the Delta variant was different from the Beta. Some of those differences might show up in terms of how contagious it is, in it’s symptoms or a combination of things. Case in point—we know that the Omicron variant is more transmissible than the others due to mutations on the virus's spike protein,, but also causes less severe disease in most people.

As a virus spreads, it has more opportunities to mutate, but by studying each variant, scientists can determine the differences and often predict if a new variant will be more dangerous than the last.

Lineage Explained

Think about your own family tree—you may be able to trace it back to 100 years to great, great grandparents, or you may have branches with close and distant cousins. Scientists study the lineage of viruses just like you draw a family tree, and  just like your family tree, the lineage of a virus is traced by finding the variants that share genetics and all come from a common ancestor.

“Think of the original strain of SARS-CoV-2 as being the ancestor. It has many lineages, and they all cause COVID-19. For example, BA.4 and BA.5 are lineages of the Omicron variant. Scientists carefully study genetic lineages in labs and in the real world to keep tabs on how the virus is changing. It helps us to respond with better treatments and prevention,” Dr. Forrester said. 


Scientists continue to monitor both existing and new strains of COVID-19, categorizing each one into a variant class. The variant class helps determine the best way to fight the virus, including vaccines, treatments and diagnostics.

Variants Being Monitored

A variant being monitored (VBM) is one that is no longer detected or is circulating only at very low levels in the U.S and no longer poses a significant threat to the American population. The CDC continues to monitor these variants to keep watch for a potential uptick. If such a shift is detected, the variant would be re-classified to a variant of interest (VOI) or variant of concern (VOC).

Think of VBMs hurricanes that have drifted offshore—meteorologists will watch them in case they re-form and come back to threaten land, but most of them continue out to sea. Current VBM variants include Alpha, Beta, Gamma, Delta, Epsilon, Eta, Iota, Kappa, Zeta and Mu.

Variants of Interest

A variant of interest (VOI) is defined as a strain that meets both the following criteria:

  • It has genetic changes that could affect how contagious it is, how sick it makes people or how well vaccines work against it.
  • It has led to increased community spread or caused clusters in multiple countries—more people are getting sick in more places. 

Currently, there are no variants classified as a VOI.

Variants of Concern

A strain is upgraded to a variant of concern (VOC) if it meets the criteria for a VOI, plus at least one of the following:

  • It is more contagious.
  • It causes more severe disease.
  • Public health measures such as vaccines, tests and treatments are not as effective.

Omicron is currently the only variant the WHO classifies as a VOC. Past VOC variants include Alpha, Beta, Gamma and Delta.

 Variants of High Consequence 

In addition to meeting the definition of a variant of concern, a variant of high concern  (VOHC) is defined by the following:

  • It isn’t detected well enough by tests or doesn’t meet testing targets.
  • There is a significant reduction in vaccine effectiveness, an unexpectedly high percentage of vaccinated people have been infected or vaccines don’t protect well against severe disease.
  • Treatments are significantly less effective relative to previously circulating variants.
  • It causes more severe disease and increased hospitalization.

No COVID-19 variants are currently designated variants of high consequence.

De-escalated Variants

Variants can also be de-escalated or downgraded from a previous status. The CDC does this when the variant no longer meets criteria for a VOI, VOC or VOHC.

Here are the reasons the new forms of SARS-CoV-2 have been downgraded:

  • The[KE2]  new form is no longer spreading.
  • It has been spreading for a long time without affecting the overall health situation.
  • Scientific evidence demonstrates that it doesn't have any concerning properties.

Currently, Delta is the only COVID-19 variant that has been downgraded from a VOC to a VBM. This means that the available data does not indicate that Delta meets the criteria for a VOI, VOC or VOHC, and is not a public health concern.

The Bottom Line?

“As always, it’s critical to stay up-to-date on your vaccines so you stay ahead of the virus,” Dr. Forrester said. “Any immunity is better than no immunity, and data clearly shows that vaccinated and boosted people are much less likely to develop severe illness or need hospital care.”