If you imagine viruses as pieces of a jigsaw puzzle, that can help explain what happens when a coronavirus variant comes into contact with human cells.
With a more contagious variant now dominant in the U.S., the country's genomic surveillance capacity is getting a major boost.
The variant known as B.1.1.7, which is more easily spread, was first identified in England last fall. Since then, it has spread quickly in the U.S.
Despite the progress in vaccinating Americans, there's concern about the threat posed by COVID-19 variants. The White House is urging not to "let down our guard."
Much of the blame for Brazil's coronavirus disaster lies with Jair Bolsonaro, who has enabled a domestic tragedy that now threatens the world, says analyst Robert Muggah.
Scientists are spotting new coronavirus variants almost on a daily basis. So far public health experts are still most worried about three important ones.