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Delta Plus is in the news again, this time because South Korea's Disease Control and Prevention Agency announced it had found earlier this week.

The variant and its subsequent lineages have been detected on U.S. soil, most recently in the Provincetown outbreak; however, for a Delta Plus sublineage. It's also been reported in several other countries, including the U.K. and India.

Experts maintain that these sublineages .

What made Delta Plus (originally known as B.1.617.2.1, now called AY.1) so concerning was that it had the K417N mutation, which led to a key change in the spike protein that's been associated with .

Now, AY.1 and two others -- AY.2 and AY.3 -- are all labeled variants of concern by both and , and they continue to be monitored within the original Delta category.

According to , the original Delta variant is estimated to account for 83.4% of all COVID infections in the U.S. as of July 31. While the estimated prevalences for AY.1 (0.1%) and AY.2 (0.8%) remain small, AY.3 accounts for an estimated 9.1% of infections, according to the tracker.

These estimates come from the CDC's National SARS-CoV-2 Strain Surveillance (NS3) program, which is based on more than 175,000 sequences collected since Dec. 20, 2020.

As for the South Korea Delta Plus cases, one occurred in a man in his 40s with no recent travel, and another occurred in a fully vaccinated person who had just returned from the U.S., the agency reported.

In its technical briefings, Public Health England refers to all the sublineages as "Delta with K417N," and has detected 45 cases as of its (39 confirmed on sequencing and six with probable genotyping).

This report noted that as of July 16, a total of 828 genomes of Delta with K417N have been identified in GISAID, with the largest numbers reported in the U.S. (592), Portugal (56), Japan (47), Switzerland (41), Poland (27), and India (23).

But the sublineages aren't raising too many alarm bells among experts just yet. British epidemiologist Colin Angus, BSc, MSc, , "To date, there is no clear evidence that it conveys enough of a benefit to the virus to allow it to dominate the original Delta variant. So although it is clearly here, there is no obvious sign that it has gained a foothold over existing variants of the virus."

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