It is estimated that more than one-third of coronavirus infections in the United States are now caused by a new, fast-growing member of the so-called “FLiRT” variant group. The FLiRT mutant strain is nicknamed because it has small but characteristic changes compared to JN.1. distortion. JN.1 was the variant behind this winter's wave of infections.
The largest of these, dubbed KP.2 by scientists, has rapidly multiplied in recent weeks to become the currently dominant strain of the new coronavirus.
KP.2 and another strain with the same FLiRT mutation, called KP.1.1, are projected to together account for 35.3% of cases this week, according to biweekly variant estimates from the U.S. Centers for Disease Control and Prevention. . This was up from 7.1% last month.
“This means that although KP.2 is proportionately the most predominant variant, it is not causing an increase in infections due to low transmission of SARS-CoV-2,” a CDC spokesperson said. he told CBS News in a statement.
The strain also shows no major changes to worry about, unlike some previously highly mutated variants that have raised alarm over the past few years.
But rapid changes in circulating variants have prompted the Food and Drug Administration to this week Citing the need for more “up-to-date” data, it is delaying a key step in the process to select strains for coronavirus vaccines this fall.
A federal requirement for hospitals to report COVID-19 data to authorities expired this month, but the CDC continues to track activity caused by the virus by collecting reliable numbers from sources such as wastewater testing and emergency rooms. He said that he is still receiving.
Here's the latest information we know about the new coronavirus disease (COVID-19) variants in the United States.
What are the current new variants of coronavirus disease (COVID-19)?
Approximately 28.2% of coronavirus cases nationwide are now caused by a sublineage of the virus called the KP.2 variant, according to the latest projections released by the CDC.
The next largest growing variant is another JN.1 descendant called JN.1.16. The strain hasn't spread as quickly, with only an estimated 10% increase in cases this week.
The projections are based primarily on the genetic sequence of the virus reported by public health institutes, which has fallen significantly in recent weeks as the overall number of infections declines. Other CDC data from wastewater and traveler testing still do not separate KP.2 from its parent, JN.1.
KP.2 is a closely related descendant of this winter's JN.1 variant, and despite having a higher number of mutations, it is less severe than the previously dominant variant. It turns out that.
“So this is something that we are watching closely and something that we are monitoring. “We reiterate the need for monitoring,” the World Health Organization said. Maria van Kerkhove told reporters on Wednesday:
Why are these COVID-19 variants called FLiRTs?
The nickname FLiRT comes from two distinctive mutations found in several descendants of the JN.1 variant that emerged around the world after raging during the winter. Some of the largest strains with FLiRT mutations in the United States today are KP.2 and KP.1.1.
“Essentially, specific amino acid changes in the spike protein F456L + R346T, from phenylalanine (F) to leucine (L) at position 456 and from arginine (R) to threonine (T) at position 346, We're just making it,'' Canadian biologist and University of Guelph professor Ryan Gregory told CBS News in an email.
Gregory coined this nickname. in marchAnd it gained attention among mutation trackers, who discovered many characteristic changes in the virus during the pandemic, giving it the nickname. Although unofficial, these nicknames have become commonly used names with many variations.
FLiRT has earned another nickname — Variations of “tiLT” It was created by Australian consultant Mike Honey. FLiRT refers to a rapidly growing collection of JN.1 derivatives that trackers are focusing on, among which is KP.2.
“Essentially, at the moment almost everything is a descendant of BA.2.86.1.1 (JN.1), and the situation is rapidly evolving, so for now we are focusing on the mutations of interest rather than the individual variants. It makes more sense to guess,” he wrote. Gregory.
Do FLiRT variants cause different COVID-19 symptoms?
The JN.1 variant, which many Americans have likely already been infected with over the winter, unlike some previous highly mutated variants that have raised concerns about possible changes in symptoms in recent years. is closely related to the currently increasing KP.2 strain.
“Based on current data, there is no indication that KP.2 causes more severe disease than other strains,” a CDC spokesperson told CBS News.
The two distinctive so-called FLiRT mutations in KP.2 were also previously seen in the XBB.1.5 variant, which was in circulation throughout 2023, the spokesperson said.
A draft study by Japanese scientists published as a preprint that has not yet been peer-reviewed found that the variant appears to be more effective at evading antibodies than the JN.1 variant. This “increased immune resistance” likely explains the increase, the scientists said.
Health officials and experts have generally downplayed claims that the variants cause different symptoms. Changes in a person's immunity due to vaccines or previous infections are often responsible for a variety of symptoms, rather than specific mutations.
“Mutations occur frequently, but only occasionally change the characteristics of the virus,” the CDC said.
Will the vaccine be effective against the FLiRT variant?
The CDC has made no changes to its current vaccine recommendations, which were last updated in April. However, the emergence of descendants of these new JN.1 variants, like KP.2, could influence which vaccines the FDA chooses this fall and winter.
Most Americans are eligible to receive at least one dose of the COVID-19 vaccine this season, and so far, CDC data shows, most Americans have been eligible for at least one dose of the COVID-19 vaccine this season, and so far, fewer patients have been able to get the vaccine in emergency departments or emergency rooms during the period when JN.1 was on the rise. It has been shown to be up to 51% effective against treatment visits. .
“CDC continues to monitor community transmission of the virus and the effectiveness of vaccines against this strain,” the agency said regarding KP.2.
World Health Organization experts last month advised vaccine manufacturers to produce vaccines that target the JN.1 variant for next season. The FDA's own panel of vaccine experts was scheduled to consider its approach to the U.S. vaccine market next week.
However, the agency recently announced It decided to postpone the meeting until June in the hope of buying more time to ensure the selection of vaccine targets “most appropriate for use against strains expected to become prevalent” in the fall.
“FDA is working with public health partners to closely monitor trends in circulating strains of SARS-CoV-2. “We have recently observed changes in the predominant circulating strain of SARS-CoV,” an FDA spokesperson told CBS News in a statement.
Pfizer is generating data from a study of its vaccine against KP.2, but a company spokesperson said it could not share the results at this time. A Moderna spokesperson did not respond to a request for comment.
A Novavax spokesperson said there is data showing this fall's vaccine candidate targeting JN.1 has “good cross-reactivity” to KP.2. Novavax's vaccine takes longer to manufacture than mRNA vaccines from Pfizer and Moderna, but the delay to the FDA meeting “will not impact” its ability to administer vaccinations this fall, a spokesperson said.
A Novavax spokesperson said: “We are manufacturing JN.1 in accordance with recommendations and expect to offer the latest vaccine this fall.”
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