Alpha, Delta and more: Why coronavirus variants are causing alarm

Scientists pay the most attention to mutations in the gene that encodes the virus's spike protein, which plays a key role in its entry into cells and is targeted by vaccines

A succession of more-transmissible SARS-CoV-2 variants has em­erged over the past year, each harbouring a constellation of mutations. The most worrisome so far is the so-called delta variant.

Is delta more virulent?

Possibly as it appears patients are more likely to be hospital­i­sed with delta than with the previously dominant alpha strain. A large UK study published in Lancet Infectious Diseases sho­wed Covid-19 patients have a 2.3 times increased risk of being hospitalised within two weeks if they have delta compa­red with an alpha infection. That fit with an earlier study from Scot­land that showed the risk of hospital admission was almost