The “plus” of the variant's name refers to its K417N spike protein mutation, which was also found in some substrains of the alpha variant — the dominant strain in the country before the delta variant — but the substrains never got a foothold, he explained.

What is the Delta variant?

The delta variant is a strain of SARS-CoV-2, the virus that causes COVID-19. According to the Centers for Disease Control and Prevention (CDC), the delta variant was first identified in India in December 2020, and it was detected in the United States in March 2021.

How much more contagious is the Delta variant of COVID-19?

• The Delta variant is more contagious: The Delta variant is highly contagious, more than 2x as contagious as previous variants.