A new sublineage of the delta variant is sweeping across the UK. This is what we know

(CNN) – UK and international authorities are closely monitoring a delta variant sublineage that is causing a growing number of infections in the United Kingdom.

This “descendant” of the delta variant, known as AY.4.2, represented 6% of cases in the week of September 27 – the last week with complete sequencing data – and is “on an upward trajectory”, according a report from the UK Health Security Agency.

There is not much information about the AY.4.2 sublineage. Some experts have suggested that it could be slightly more transmittable than the original delta variant, although this has yet to be confirmed. While it is responsible for a growing number of infections, it is not yet classified in the UK as a ‘variant of concern’. It remains rare outside of Britain today, with a small number of cases reported in Denmark and the US, expert Francois Balloux told the Science Media Center (SMC) on Tuesday.

“As AY.4.2 is still quite low in frequency, a 10% increase in its transmissibility could have caused only a small number of additional cases. Therefore, it has not driven the recent increase in the number of cases in the UK. “, declared Balloux, professor of Biology of Computational Systems and director of the Institute of Genetics of the UCL, to the SMC.

While the new variants have overtaken each other to become the dominant strain globally in the last year, experts say it is too early to know if the AY.4.2 sublineage will be significant. In the UK, “the delta variant rapidly outperformed within weeks” the alpha variant during the summer, Deepti Gurdasani, Professor of Epidemiology at Queen Mary University of London, told CNN. “That is not what we are seeing here, we see a kind of slow increase in the ratio that suggests that it is not enormously more transmissible, it could be slightly more transmissible.”

Balloux agreed and told SMR that “this [es] a situation not comparable to the appearance of the alpha and delta variants, which were much more transmissible (50% or more) than any strain in circulation at that time. This is a small potential increase in transmissibility that would not have a comparable impact in the pandemic. “

The AY.4.2 sublineage has caught the attention of public health experts across the pond. In a series of tweets on Sunday, Former US Food and Drug Administration (FDA) Commissioner Dr. Scott Gottlieb called for an “urgent investigation” into this subtype of the delta variant and said it was a “reminder that we need robust systems to identify and characterize new variants. “

However, the emergence of the AY.4.2 sublineage in Britain points to what scientists have warned throughout the pandemic: increased transmission can create new variants. The UK has had the highest daily rate of COVID-19 cases and deaths per million people in Western Europe since most of the pandemic restrictions were lifted in the summer. On Tuesday, it reported 223 deaths from covid-19, the highest daily figure since the beginning of March, and health leaders are urging the government to reinstate measures such as the obligation to wear masks in closed spaces to help relieve pressure on the health system. .

The whole ‘problem with this approach of living with the virus and allowing 30,000 to 50,000 cases a day, which has been the UK case rate since [el verano], is that evolution [del virus] will continue … we have to suppress the cases and suppress the virus, “Gurdasani said.