Mutant Covid variant 'FLiRT' even more resistant to human immune systems: report

Covid is out with a new variant this spring that are even more able to infect healthy cells. KP.1.1 and KP.2, collectively known as the "FLiRT" variants, have mutations in their spike proteins that appear to make them more capable of penetrating the human immune system, but there is no evidence as of yet that this will lead to more severe illness.

According to the latest data from the Centers for Disease Control, KP.2 accounted for nearly 25 percent of all new cases in the US in April, overtaking JN.1, which had been the dominant strain for months. 

The proportion of infections identified as KP.1.1 also grew, with the variant making up 7.5 percent of overall cases.

Both KP.1.1 and KP.2 are descendants of BA.2.86, better known as Omicron, which was itself a great grandchild of the original strain. Omicron and its sub-variants have proven themselves to be less harmful than their predecessors, and as a result, the CDC has relaxed the guidelines for those who test positive.

Nonetheless, experts have warned that those who are elderly or immunocompromised should still stay up to date with their vaccines.

As the Daily Mail reports, researchers from Japan and the United Kingdom, who first looked into the new strains, noted that KP.2 has at least three "substitutions" in its spike protein that differentiate it from JN.1, thus giving it, and KP.1.1 "higher viral fitness."

In an interview with the outlet, infectious disease doctor and University of Buffalo professor Thomas Russo explained that "Once they evade those defenses," he said, "their infectiousness is not quite as great as some of the earlier variants, but obviously the ability to evade our defenses [has] been enough where it's increasing in proportion."

Russo warned that, as a result, while the new strains will likely present little threat to young, healthy individuals, infections in those with comorbidities could lead to a spike in hospitalizations.