A vaccinated person's guide to the most concerning COVID-19 strains

Though they are technically not alive, viruses are not unlike living plants or animals. They can be bred, and they can mutate; over months and years, they evolve into new things. At some point in November 2019, there was one human on Earth who had been infected with SARS-CoV-2. Now, the virus has passed through millions of bodies, and replicated trillions of times. It is the nature of RNA viruses to change and evolve gradually — thus, the SARS-CoV-2 virus that infected patient zero has spawned numerous variants as it multiplied through the human population.

"All RNA viruses mutate over time, some more than others," writes Robert Bollinger, a professor of Infectious Diseases at Johns Hopkins University." For instance, flu viruses are particularly prone to mutation, which is why new strains circulate every year.

The novel coronavirus's variants have sprung up all over the world, with some of the most prominent mutations appearing in England, South Africa, Brazil, India and California. As long as the coronavirus keeps spreading, it will keep mutating, which is why public health experts are pushing vaccination as a means to stop the spread and thus the mutations.