Infections with the COVID-19 virus can be caused by a number of different genetic changes in the virus. These are called variants. Scientists track the changes in the COVID-19 virus because they can affect how easy the virus spreads, which strains cause more severe disease and whether vaccines or medicine work against them.
Over time, the COVID-19 virus has changed and spread globally. Virologists identify these changes using a process called mapping the genetic material of viruses (known as sequencing). Variants are considered significant when they show an increase in transmissibility, increased virulence or reduced effectiveness of vaccines and medicines against them.
The most common type of COVID-19 infection comes from the delta variant, which was first detected in India in late 2020. Then came Alpha, which had a number of mutations that made it more contagious than the delta variant. It also evaded people’s immune systems better than the delta variant, making it harder for them to tell when they have been infected.
Vaccines and antiviral drugs are the best ways to prevent COVID-19 infections. But new variants can emerge and change the way that COVID-19 infections occur, so public health officials constantly monitor the outbreak and take steps to respond quickly.