What scientists know about new, fast-spreading coronavirus variants
Key questions remain about how quickly B.1.617 variants can spread, their potential to evade immunity and how they might affect the course of the pandemic.
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 foothold. Key questions remain about how quickly the variants can spread, their potential to evade immunity and whether they cause more severe disease.
A lot of this research takes the form of standard epidemiology — confirming COVID-19 cases through testing, identifying the variants responsible for infections and cross-referencing these data to people’s clinical symptoms and vaccination statuses. Scientists can also glean insights from genomic-sequencing data, identifying which mutations are present in the B.1.617 subtypes and comparing these with mutations in earlier variants whose behaviour is better understood.
“I look at individual mutations because they each have individual properties that we think might confer higher transmissibility,” says Julian Tang, a consultant virologist at the Leicester Royal Infirmary, UK. Increased transmissibility — a measure of how quickly variants can spread from person to person — could accelerate outbreaks, which could put more pressure on health-care systems and counter-measures such as vaccination programmes. For example, the B.1.617.2 variant has mutations called 452R and 478K, which Tang says are both linked to increased transmissibility. Both mutations alter the spike protein, which the virus uses to enter human cells.