What you need to know – DW – 19.09.2024

During the European summer, the number of COVID-19 infections increased again. The number of positive SARS-CoV-2 tests was over 20%. Worldwide, the number of positive tests was around 10%.

The United States also appears to have seen an increase in hospital admissions following a wave of COVID-19 infections in Singapore.

Now that fall and winter are entering the Northern Hemisphere, there are concerns about two new variants.

The first is known as KP.3 and its subvariant KP.3.1.1. The second is XEC, a “recombinant” variant related to KP.3.

The U.S. Centers for Disease Control and Prevention (CDC) considers KP.3 a global variant of concern (VOC) in the United States because KP.3 was “predominant” there in August. VOCs may spread more easily or cause more severe illness.

It is important to note that KP.3 is not a global VOC, but only exists in the United States.

The CDC recommends that people get vaccinated with a current COVID-19 vaccine in 2024-2025.

What are the KP.3 and XEC variants?

KP.3 belongs to a group of SARS-CoV-2 variants known as FLiRT variants. SARS-CoV-2 is the basic virus that causes the disease COVID.

As the name KP.3 suggests, there are also subvariants KP.1 and KP.2. KP.3 prevailed because it is more contagious than other circulating subvariants.

KP.3 and other FLiRT variants originate from the omicron variant of SARS-CoV-2.

Now think of a family tree: The KP variants are children of the variant JN.1. And JN.1 is in turn a child of the omicron variant BA.2.86.

This is important to know because of all the major COVID variants, Omicron remains dominant worldwide. You will recall that other major variants are Alpha, Beta, Delta and Gamma.

But Omicron is constantly evolving or mutating into new variants and subvariants.

It is believed that the subvariant XEC was created when KP.3 merged with KS.1.1, but we don't know for sure.

As Francois Balloux, professor of computational systems biology and director of the UCL Genetics Institute in the UK, explained to the Science Media Centre, “XEC is probably a recombinant between the subvariants KP.3.3 and KS.1.1.”

XEC-COVID variant in Germany

XEC was reportedly first detected in Germany in June. However, it does not yet appear on the Robert Koch Institute's COVID dashboard.

As a spokesperson for the Robert Koch Institute leaked via email, XEC may never appear on the dashboard because “it is not possible to predict how individual variants will spread.”

Since June, the number of XEC cases in Germany has been in the double digits, but the spokesperson did not elaborate. The RKI does not even mention XEC in its weekly evaluation of September 18, 2024.

In Germany, the focus remains on KP.3.1.1, which is dominant and is considered more contagious than earlier variants.

Virologist Sandra Ciesek told the DPA news agency that it was no surprise that KP.3.1.1 was more contagious.

“The virus is constantly mutating in search of new ways to infect people […] But that does not mean that the variant causes a more severe course of the disease,” says Ciesek from the German Center for Infection Research.

How common are KP.3.1.1, KS.1.1 and XEC?

As of September 3, KP.3.1.1 remained the predominant variant, according to data provided by GISAID, the Global Initiative on Sharing All Influenza Data, and presented by outbreak.info.

• KP.3.1.1 has been detected worldwide 14,396 times
• KP.3.3 has been detected worldwide 9,157 times
• KS.1.1 has been detected worldwide 2,650 times
• XEC has been detected worldwide 95 times

How dangerous are the FLiRT variants?

Paul Hunter, a professor of medicine at the University of East Anglia in the UK, told DW in August that “FLiRT” was a “silly” acronym “but one that has caught on,” and one with a serious meaning.

FLiRT refers to mutations at key sites in this all-important spike protein – the protein that allows the virus to insert itself into a living cell, infect it, and then replicate and spread.

FLiRT variants appear to be potentially more dangerous than earlier versions of SARS-CoV-2.

A paper published in July 2024 noted that KP.2 “has a greater ability to evade vaccine-induced immunity” and replicates more effectively than its “parent” variant JN.1.

As for KP.3, the CDC said its subvariant KP.3.1.1 was likely responsible for 30-40% of clinical COVID-19 samples in the U.S. by mid-August 2024. This indicates a rapid increase from a rate of 20-26% two weeks earlier, at the beginning of the same month.

The risks associated with KP.3.1.1 are particularly acute for people over 65 years of age and children under two years of age, the CDC said.

Edited by: Fred Schwaller

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COVID-19 variant update via the U.S. Centers for Disease Control and Prevention and the Infectious Diseases Society of America