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New COVID-19 variants KP.3 and LB.1 are gaining traction across the U.S., especially in the western region, where a noticeable uptick in emergency room visits for COVID-19 has been reported.

The variants have emerged as the latest contenders to dominate the pandemic landscape, contributing to a new surge of infections that is arriving earlier than last year, according to the Centers for Disease Control and Prevention (CDC).

For the first time in months, the CDC reports no states or territories have seen a decline in COVID-19 infections this past week. The resurgence is most pronounced in western states, where virus levels detected in wastewater are nearing the CDC's "high" risk threshold. Additionally, nursing home cases in the region have seen a sharp increase, per CBS News.

In HHS Region 9, which includes states from Arizona to Hawaii, COVID-19 patients accounted for an average of 1.23% of emergency room visits last week. This figure represents the highest average of such visits in the region since early February, indicating a significant rise in the severity of cases.

Historically, COVID-19 surges have followed a springtime lull, typically increasing during the warmer months. However, the current spike, occurring earlier than last year's late July rise, coincides with the growing prevalence of KP.3 and LB.1 variants. The CDC's Nowcast projections indicate that KP.3 has increased to roughly a third of cases nationwide, up from 25% two weeks ago, while LB.1 now constitutes 17.5% of cases.

LB.1 appears to be growing faster than KP.3, suggesting it might become the dominant strain. These variants, along with their predecessor KP.2, which rose to prominence last month, share a common ancestor in the JN.1 strain, responsible for last winter's case surge. Early research suggests that a mutation unique to LB.1, identified as S, could contribute to its rapid spread.

Dr. Peter Marks of the FDA noted the agency's recent decision to prioritize KP.2 for the updated fall vaccine, aimed at improving protection against the evolving strains. Despite this decision not being based on "iron-clad evidence," it reflects an effort to align vaccine formulations more closely with circulating variants.

The exact severity of KP.3 and LB.1 remains under investigation, as the CDC continues to monitor their impact. Preliminary lab findings from Japan indicate that LB.1 may possess enhanced transmissibility due to its unique mutation.

Health officials and the public await more detailed data to better understand the potential implications of these variants and the effectiveness of upcoming vaccines. The rising trend underscores the need for vigilance and adaptability in the ongoing battle against COVID-19 after the pandemic.