What scientists know about new, fast-spreading coronavirus variants

Since the SARS-CoV-2 variant known as B.1.617 was first reported in India late last year, it has spread to dozens of other countries — including the United States, Singapore and the United Kingdom, where it has become dominant in some regions.

Researchers have since identified three subtypes, known as B.1.617.1 (the ‘original’ B.1.617), B.1.617.2 and B.1.617.3, each with a slightly different genetic make-up.

They are now rushing to investigate these variants and work out how they might affect the trajectory of the pandemic in countries where they have gained a...