WASHINGTON — For weeks, scientists have watched a multitude of omicron descendants struggle for dominance of COVID-19 transmission in the United States, with BQs (BQ. 1 and BQ. 1. 1) appearing to outperform the others in claiming a slight advantage.
The result has been a slow accumulation of cases and hospitalizations that never reached the peaks of this summer’s BA. 5 wave and, in fact, had nothing to do with the tsunami of disease caused by the original omicron strain a year ago.
But on Friday, the U. S. Centers for Disease Control and Prevention’s COVID-19 variant dashboard was on the verge of COVID-19 variants. The U. S. revealed a new black horse that could soon take the field by storm: XBB. 1. 5.
The CDC estimates that XBB. 1. 5 has more than doubled its share of the COVID-19 pie each week for the past 4 years, from about 4% to 41% of new infections in the month of December. In the Northeast, the CDC estimates, XBB. 1. 5 is to blame for 75% of new cases.
“In a few months, we haven’t noticed a variant takeoff at this speed,” said Pavitra Roychoudhury, director of COVID-19 sequencing at the University of Washington School of Medicine’s Virology Laboratory.
Virologists and epidemiologists say this omicron sublineage has characteristics that give it the possibility of causing a new wave of COVID-19 cases in the U. S. It’s not yet clear how big that wave will be and whether it can send many more people. to the hospital.
Despite all the recent considerations that a new COVID-19 risk may come from China’s continued rise, experts note that XBB. 1. 5 appears to have appeared in the U. S. UU. Se first detected in New York and Connecticut in late October, according to GISAID, a global effort to catalog and track variants of the coronavirus.
Trevor Bedford, a professor of computational biology at the Fred Hutchinson Cancer Center in Seattle, said XBB. 1. 5 has an expansion rate to its remote cousin BA. 5.
Bedford set its effective aftershock rate (the number of new infections expected to be caused by the irritated user) at about 1. 6, about 40 percent higher than its next closest competitor.
“I expect this to lead to increased flow in the coming weeks,” Bedford wrote in an email. This increase may not be reflected in the number of cases, he said, as more people check at home. And your cases may not be counted unless you see a doctor and have lab tests to verify your results. “Therefore, I would consider hospitalizations in vulnerable age teams (such as the elderly) as an indicator of higher wave,” he wrote.
Slippery subvariants
XBB. 1. 5 is the product of recombination: two descendants of BA. 2, the subvariant that caused a modest wave of cases in the United States in April, swapped parts of their genetic code, resulting in 14 new mutations in the virus’ spike proteins for BA. 2, and a new sublineage, XBB.
XBB led a wave of instances in Singapore this fall, but never gained much traction in the United States. Here, it had to compete with a multitude of co-circulating variants that had independently evolved some of the same mutations, making them more equal.
Still, scientists are keeping an eye on XBB and its consequences.
Dr. David Ho, a professor of microbiology and immunology at Columbia University, recently tested viruses designed to have the peaks of XBB and XBB. 1 such as BQ. 1 and BQ 1. 1 in his lab as opposed to antibodies from the blood of inflamed people, who have been vaccinated with the original, novel bivalent vaccines. and that they had been inflamed and vaccinated. His team also tested 23 monoclonal antibody remedies opposed to those new sublineages.
He found XBB. 1 to be the most slippery of them all. It is 63 times less likely to be neutralized through antibodies in the blood of other infected and vaccinated people than BA. 2 and 49 times less likely to be neutralized than BA. 4 and BA. 5.
In terms of immune evasion, Ho says, those variants have moved as far away from the antibodies we created to use as the original omicron variant came from the COVID-19 viruses that preceded it about a year ago.
He calls those degrees of immune evasion “alarming” and said they can still compromise the effectiveness of COVID-19 vaccines. Their findings were recently published in the journal Cell.
Ho said Monday that XBB. 1. 5 is the same story in terms of antibody evasion as XBB. 1, it has the potential to evade vaccine protections and beyond infections. It is also resistant to all existing antibody treatments, Evusheld added.
Another trick up your sleeve
In addition to being highly immune, XBB. 1. 5 has an extra trick up its sleeve that turns out to boost its growth. It has a key mutation at site 486, allowing it to bind more strongly to ACE2, the gates the virus uses to enter. our cells.
“The XBB. 1. 5 mutation spreads better,” Jesse Bloom, a computer virologist at the Fred Hutchinson Cancer Center, wrote in an email.
This mutation was first reported by Bloom, who studies the evolution of viruses and viral proteins as likely vital for viral fitness. This was shown by Yunlong Cao of Peking University.
“It has a greater ability to enter cells,” Roychoudhury said, meaning it’s more contagious.
Still, experts say it’s hard to know how much of XBB. 1. 5’s spread can be attributed to households from the virus and how much to the right timing.
Going off the holidays, when other people were more likely to socialize, gives more leeway to any infection, whether it’s flu, COVID-19, or RSV.
“Most public fitness officials would have expected a backlog of COVID-19 cases, even before we knew XBB. 1. 5. “said Andrew Pekosz, a professor at Johns Hopkins’ Bloomberg School of Public Health who studies viral replication.
“So whether the increases in COVID cases that occur during the holidays are decreasing because of social interactions that other people have had or if they are particularly similar to XBB. 1. 5, there is still something that is unclear. Both are probably contributing,” Pekosz said.
Most experts have said that while they expect XBB. 1. 5 to have the potential to cause more illness, they don’t expect those infections to necessarily be more serious.
“More immunity in the population”
Looking northeast, where XBB. 1. 5 is thought to be the source of most infections, Michael Osterholm, who directs the Center for Infectious Disease Research and Policy at the University of Minnesota, sees an explanation for the hope.
Osterholm notes that the updated boosters provide some protection, even against this highly immune evasive strain.
“They still provide a point of immunity that possibly wouldn’t save you from getting infected, but it can have a significant effect on whether or not you get seriously ill and die,” he said. “I mean, right now, the peak recent knowledge we have shows that those who have the bivalent vaccine have a three times lower risk of death than those who don’t. “
However, the Americans have been slow to get the new reinforcements. According to CDC data, only 15% of eligible Americans have had an updated recall. Date of vaccination.
Experts also note that antibody remedies do not oppose this sublineage, other antivirals, such as Paxlovid and remdesivir, deserve to remain effective.
Rapid testing continues to work, as do masks, ventilation, and indoor air filtration, so even if the virus continues to evolve, there are still smart tactics in place to oppose COVID-19.
“It doesn’t seem to be causing more severe disease, so I think the scenario circulating today is very different from a year ago,” Osterholm said. “There’s a lot more immunity in the population than I don’t think so. “It’s going to take off. “