Most viruses tend to constantly change structure due to mutations that produce new variants of the virus. Like other viruses, the COVID-19 virus or SARS-CoV-2 exists in several variants. Over the years, the most common variants of concern for the COVID-19 virus have been the alpha, beta, gamma, delta, and Omicron variants.
In late 2020, the delta variant was identified in India and was subsequently detected in approximately 77 countries, including the U.S. The delta variant was characterized by mutations in its S protein. Several of these mutations were thought to have affected the immune response and could have caused a potentially higher transmission rate than other variants. For a period of time, the delta variant was responsible for most of the new COVID-19 cases in the U.S.
A subvariant of the delta variant called the “delta plus” variant was also identified and appeared to have a mutation that allowed the virus to attack lung cells and potentially escape existing vaccines more effectively.
Currently, various Omicron variants are considered variants of concern and interest.
