Delta Plus Sub-Variant, Possibly More Contagious Than Delta, Found in These Countries

The Delta AY.4.2 COVID sub-variant, which has sparked interest recently due to its rise in the U.K., has been found around the world in 27 countries.

The data, from the GISAID virus reporting database and collected and displayed by Outbreak.Info, shows the variant is almost totally limited to the U.K. but that cases have been reported in the U.S., Canada, Australia, and parts of western Europe.

Of the 14,970 AY.4.2 cases to have been sequenced worldwide from October 18, some 14,247 were from the U.K. The country with the next highest prevalence is Romania, followed by Poland, Ireland, and then Denmark.

Some countries, such as Australia and Japan, have only reported one case. The U.S. has reported a total of three, while Canada has reported six.

The number of AY.4.2 cases has sharply increased in the U.K. since July this year, Outbreak.Info shows, and accounts for between seven and eight percent of new sequenced cases there.

The graph shown below, compiled by the U.K.'s Wellcome Sanger Institute using data from the COVID-19 Genomics U.K. Consortium, shows the rise of the COVID Delta variant in light blue starting around mid-April.

It then shows how Delta AY.4.2 cases, highlighted in light brown, are beginning to creep up.

AY.4.2 graph
A graph from the Wellcome Sanger Institute using COVID-19 Genomics U.K. Consortium data showing how AY.4.2 sequences, represented in light brown, have increased in the U.K. recently. Contains public sector information licensed under the Open Government Licence v3.0. Wellcome Sanger Institute

AY.4.2 is a branch of the Delta AY.4 variant, which itself is a branch of the original Delta. AY.4.2 is characterized by two mutations in its spike genome: Y145H and A222V.

Scott Gottlieb, former commissioner of the U.S. Food and Drug Administration from 2017 to 2019, noted the variant's U.K. rise in a series of tweets over the weekend and said it warranted "urgent research" to find out whether it is more transmissible or has any resistance to immunity.

UK reported its biggest one-day Covid case increase in 3 months just as the new delta variant AY.4 with the S:Y145H mutation in the spike reaches 8% of UK sequenced cases. We need urgent research to figure out if this delta plus is more transmissible, has partial immune evasion?

— Scott Gottlieb, MD (@ScottGottliebMD) October 17, 2021

Gottlieb also referred to AY.4.2 as a "Delta plus" variant. The term Delta plus was used earlier this year to refer to Delta offshoots with the K417N mutation. It's unclear if this term is interchangeable. Many scientists are referring to it simply as AY.4.2.

On October 15 the U.K. Health Security Agency released a technical briefing in which it confirmed AY.4.2 was "noted to be expanding in England" and that the variant was being assessed.

The variant is not currently listed as a distinct variant of concern or a variant of interest by the U.K., World Health Organization, or the U.S. Centers for Disease Control and Prevention (CDC).

In a tweet over the weekend, Francois Balloux, director of the Genetics Institute at University College London, estimated AY.4.2 could have a transmissibility advantage of around 10 percent over its parent variant.

Professor Christina Pagel, a mathematician at University College London, who specializes in mathematical modeling for health purposes, previously told Newsweek: "I don't think there's a reason to think AY.4.2 is disastrous—10 percent advantage isn't great but it's not nearly as bad as what Delta had over Alpha for instance... but the next substrain could be!"

Correction 7:17 a.m. EDT 10/20/2021: This article has been updated to correct how many countries AY.4.2 has spread to.

COVID swab
A health worker holds a swab from a COVID PCR test in London, England, in November 2020. The Delta AY.4.2 variant has been spreading in the U.K. recently. Leon Neal/Getty