United States: The concerns linked to COVID-19 have been raised again, and this time, it is not the FLiRT variant – it is due to the LB.1 variant, which has been dubbed as “D-FLiRT.” The emerging evidence linked to the LB.1 variant shows that it is the most transmissible subvariant as compared to other subvariants of the Omicron variant.
However, the health experts have not commented on the severity of the disease.
COVID Variants – from XBB to FLiRT to FLuQE
The health experts have mentioned that the concerns linked to COVID-19 infection have been increasing with transmission reported in the variants of the infection. The XBB.1.5 variant resulted in the wave around the world in 2023, according to the reports published by The Conversation.
It is to be noted that the current COVID vaccine is effective against the XBB.1.5 variant. In August 2023, the JN.1 variant was discovered, and it was the only variant that did not have small genetic changes.
In an unexpected turn, JN.1 was marked by 41 mutations from XBB.1.5, a phenomenon known as a genetic shift. These significant alterations predicted JN.1’s rapid spread, leading to another wave of infections in Australia and globally towards the end of 2023 and the onset of this year.
Subsequently, JN.1 evolved, giving rise to the “FLiRT” subvariants such as KP.1.1, JN.1.7, and KP.2.
Proteins, including the spike protein on the virus’s surface, comprise amino acids, the molecular building blocks. Scientists sequence new variants to determine the exact amino acid sequence of the spike protein, as changes here can alter the virus’s behavior.
Each amino acid is represented by a letter. The FLiRT variants were named for two genetic mutations in the spike protein: a change from phenylalanine (F) to leucine (L) at position 456 (mutation F456L) and from arginine (R) to threonine (T) at position 346 (R346T).
Preliminary research suggests these genetic changes improved the FLiRT subvariants’ ability to evade immune responses but slightly reduced their efficiency in binding to cells once inside the body.
The FLiRT subvariants have further mutated, producing new subvariants called FLuQE, including KP.3, which, along with KP.2, is currently predominant worldwide.
These variants share similarities with FLiRT but have additional genetic mutations. One such mutation is Q493E, giving rise to the name FLuQE. Alongside another mutation, F456L, these changes appear to enhance the virus’s binding efficiency, compensating for the reduced infectivity seen in FLiRT.
From FLiRT to LB.1
Reports indicate that LB.1 was first detected in March 2024. LB.1 is similar to the FLiRT subvariants but includes an additional mutation in the spike protein called S: S31del. The “del” signifies a deletion—a genetic alteration where a part of the virus’s sequence is lost during replication. In this case, the 31st amino acid (serine) in the spike protein is removed.
This variant has earned the nickname “D-FLiRT” or “DeFLiRT.” This term also applies to other variants with the same FLiRT mutations and this deletion, such as KP.2.3, as per The Conversation.
Preliminary results from research at the University of Tokyo, involving modeling and laboratory experiments, suggest that LB.1 and KP.2.3 may have higher transmissibility than both KP.2 and KP.3.
Should we be concerned about LB.1?
LB.1 has been identified in multiple countries, including Australia, and is under close surveillance by organizations like the World Health Organization and the CDC.
In the United States, as of July 15, KP.3 accounted for about 37% of cases, KP.2 for 24%, and LB.1 for another 15%, with the latter steadily increasing in recent weeks.
Reportedly, in Australia, KP.3 and its descendants, such as KP.3.2 and KP.3.2.1 (FLuQE subvariants), dominate, accounting for at least 50% of cases. The proportion of LB.1 cases remains uncertain, but it could increase over time.
Although COVID cases have been declining after a recent wave in Australia, LB.1 may eventually surpass KP.3, potentially causing another surge in cases.
The positive news is that there is no evidence suggesting LB.1 causes different symptoms or more severe illness than previous Omicron subvariants, as per The Conversation.
Current vaccines based on XBB.1.5 should provide some cross-immunity against LB.1, and oral antivirals like Paxlovid and Lagevrio should remain effective. An updated vaccine based on KP.2 is likely to be available towards the end of the year, offering better protection against these new subvariants due to their genetic similarity to KP.2.