What we know about the ‘kraken’ covid variant XBB.1.5 and why it’s causing concern

A new covid-19 variant that first was detected last year quickly has become the dominant strain in the U.S.

Nicknamed the “kraken variant” by some, it surged through the nation and now has been identified in at least 28 other countries, according to the World Health Organization.

Here are your questions, answered.

What is the new variant?

XBB.1.5 is a descendant of the omicron XBB subvariant, which is itself a cross between two earlier strains: BA.2.75 and BA.2.10.1.

The original XBB variant already has caused waves of infection in countries including Singapore and India since the WHO first raised concern about it last October.

How fast is XBB.1.5 spreading?

While accounting for just 1% of all covid-19 cases at the start of December, estimates from the U.S. Centers for Disease Control and Prevention show that it surged to become the dominant strain by the end of the month, responsible for about 41% of all infections. In northeastern states, that figure has jumped above 70%.

XBB.1.5 is “the most transmissible subvariant which has been detected yet,” said WHO’s covid-19 technical lead, Maria Van Kerkhove, during a news conference on Jan. 4. While only 29 countries have reported cases caused by it, health authorities are warning it could be much more widespread and silently proliferating thanks to a drop-off in testing.

Is it more dangerous than previous variants?

There haven’t been significant differences in severity reported between cases caused by XBB.1.5 and previous variants. Like other strains that concerned scientists, however, XBB.1.5 is attracting attention because it is exhibiting signs of immunity escape. That means it has an ability to evade natural immunity or previous protection provided by vaccines, and reinfect people who have recovered from an earlier bout of covid-19.

Where did the ‘kraken’ name come from?

The last Greek-named variant, omicron, emerged more than a year ago and left no room for the emergence of other, significantly different strains.

That has led to the rise in popularity of informal nicknames, including “kraken.” The moniker for XBB.1.5 was proposed by an evolutionary professor on Twitter to match the strength of the new strain with the mythological sea monster.