Higher transmissibility, severity: What makes delta virus strain worrisome?

 The best solution against the variant, first identified in India, is to test, isolate positive cases and vaccinate, says Sam Fazeli.

As nations race to roll out vaccines in the global effort to contain Covid-19 and allow for a return to normal, the rise of dangerous virus variants threatens to prolong the pandemic. In the U.K., the spread of the so-called delta variant, first identified in India, has led officials to send military personnel to hotspots and prompted the government to reconsider easing Covid restrictions on June 21 as planned. Here, Sam Fazeli, a Bloomberg Opinion contributor who covers the pharmaceutical industry for Bloomberg Intelligence, answers questions about the risks stemming from this variant and more. The conversation has been edited and condensed.

What sets the delta variant apart from other variants and what makes it so concerning?
The Sars-Cov-2 delta variant, also known as B.1.617.2, is a so-called variant of concern like others we have seen before including “alpha”(first found in the U.K.), “beta” (first identified in South Africa) and “gamma” (discovered in Brazil). Two factors set delta apart and make it potentially the most dangerous to date: First, it has about a 40% higher transmission rate compared with alpha, which already had a 50% higher transmissibility than the original strain of the virus. This is clearly visible in the data coming out of the U.K., which shows that the delta variant went from accounting for 1% of all cases in early April to 70% by mid-May. It will likely almost completely replace the alpha variant by the end of June.

The higher transmissibility is also clear from the increase in the number of cases across the U.K. Second, it is also believed to cause more severe disease than alpha, translating to a further rise in the percentage of positive cases that require hospitalization, despite the fact that the infections are in younger people. This second problem of increased severity had not been confirmed with any other variant to date.