Health experts warily eye XBB.1.5, the latest omicron subvariant

Three years into the pandemic, the coronavirus continues to impress virus experts with its swift evolution.

A young version, known as XBB.1.5, has quickly been spreading in the United States over the past few weeks. As of Friday, the Centers for Disease Control and Prevention estimated that it made up 72 per cent of new cases in the Northeast and 27.6 per cent of cases across the country.

Also Read: Omicron's XBB most prevalent sub-lineage circulating all over India: INSACOG bulletin

The new subvariant, first sampled in autumn in New York state, has a potent array of mutations that appear to help it evade immune defenses and improve its ability to invade cells.

“It is the most transmissible variant that has been detected yet,” Maria Van Kerkhove, the Covid-19 technical lead at the World Health Organization, said at a news conference Wednesday.

XBB.1.5 remains rare in much of the world. But Tom Wenseleers, an evolutionary biologist at KU Leuven in Belgium, expects it to spread quickly and globally. “We’ll have another infection wave, most likely,” he said.

Advisers at WHO are assessing the risk XBB.1.5 poses. Jacob Lemieux, an infectious disease doctor at Massachusetts General Hospital, said the surge in cases would not match the first omicron spike Americans experienced a year ago. “Is it a Category 5 hurricane?” he said. “No.”

Also Read: Need for second booster dose of Covid vaccine not in Centre's agenda

Still, he warned XBB.1.5 could worsen what is already shaping up to be a rough Covid winter as people gather indoors and don’t receive boosters that can ward off severe disease.

Dr. Ashish Jha, the White House Covid response coordinator, said the Biden administration was monitoring the emergence of XBB.1.5 and urging people to take advantage of existing countermeasures. Preliminary studies suggest bivalent vaccines should provide decent protection against XBB and its descendants. Paxlovid will also remain effective at fighting infections.

“We feel pretty comfortable that our countermeasures are going to continue to work,” Jha said. “But we’ve got to make sure people are using them.”

One thing Lemieux and other experts are confident about is that XBB.1.5 is not the last chapter in the coronavirus’s evolution. In fact, they expect a descendant of XBB.1.5 may soon gain mutations that make it even better at spreading.

That descendant may already exist, infecting people without raising notice yet. But sequencing efforts have declined so much worldwide that the discovery of the next generation of XBB.1.5 may be delayed.