Alpha and beta kicked off the 2021 year, and several worrisome variants later, omicron closed it out. How omicron may come to define the pandemic’s future remains uncertain. But even as omicron comes on strong, one variant, which rose to global dominance midyear in a way variants like alpha and beta never did, continues to largely define the pandemic right now: delta.
Things had actually seemed to be looking up in some parts of the world in the late spring and early summer of 2021, a year and a half into the COVID-19 pandemic. In the United States, for instance, millions of people were vaccinated, cases of the disease were falling, and people were beginning to socialize and resume normal activities.
But then delta hit hard. First spotted in India in October 2020, this variant of SARS-CoV-2, the coronavirus known as COVID-19, quickly swept around the world, supplanting other versions of the virus in 2021. Delta overwhelmed health care systems, tore through unvaccinated populations and showed that even the vaccinated were vulnerable, causing some breakthrough cases.
It soon became clear why delta wreaks so much havoc. People infected with delta make more of the virus and spread it for longer than people infected with other variants, researchers reported in Clinical Infectious Diseases in August. As a result, delta infections are more contagious. Consider two scenarios in a community where no one has immunity to the coronavirus: A person infected with an earlier version of the virus — the one first identified in Wuhan, China, that set off the pandemic — might spread it to two or three others. But a person infected with delta may transmit it to five or six people.
Mutations similar to delta’s have appeared here and there in other variants that proved themselves capable of spreading more easily or better evading the body’s immune defenses than the original virus. That includes alpha, first spotted in the United Kingdom; beta, first characterized in South Africa; and gamma, first noted in Brazil. The recently discovered omicron variant, first described in South Africa and Botswana, also shares some of the same mutations.
Some of delta’s grab bag of mutations are identical to those found in other variants, while others change the same protein building block, or amino acid, in a different way or pop up in the same part of the virus. For instance, alpha and omicron also have the same mutation of the 203rd amino acid in the N protein, but it is a different amino acid change than seen in delta. And some mutations are entirely new to delta.
These mutations on the coronavirus’ spike protein are what define delta as delta. The spike protein helps the coronavirus attach to and enter human cells penetrating host cells and cause infection. Spike proteins as learned in AP Biology while talking about COVID-19, a spike protein is a protein that forms a large structure known as a spike or peplomer projecting from the surface of an enveloped virus. The delta variant’s version carries a unique collection of mutations, marked by yellow dots in this 3-D rendering. Some of these mutations may help the virus more easily infect cells or hide from antibodies.
Though more recently in 2022 most of the population is getting the omicron variant, we must not forget the dominant variant that took control of the world and harmed a lot of people within a very short frame of time. Just when we thought we were out of the woods of COVID-19 during the summer of 2021, the delta variant proved us wrong.