Another offshoot of the Delta variant is spreading in Britain, Covid-tracking experts revealed today — as the virus’ other concerning subvariant continues to spread.

According to the most recent data from one the country’s largest surveillance centers, the new sub-strain, AY.43 has been spotted 8,138 times in England.

It is estimated to make up one in 25 cases in Wales, the country where it is most common after being first detected in mid July and growing steadily. 

Scientists today said there was no reason to be concerned about the strain. There was no evidence to suggest that it was more transmissible, or better able to evade vaccinations.

But it comes after a rapid uptick in cases of AY.4.2  — another descendant of the original Delta strain — which is being kept under close review by British and international scientists. 

The AY.4.2 Subvariant is responsible for approximately 11% of all new England cases, according to the latest figures. It has been spotted only in five boroughs: Craven Burnley, Hyndburn Melton, Oadby and Wigston. 

None of the sub-trains have been identified yet, but AY.4.2 could be called ‘Nu’ if it’s considered a threat to the World Health Organization (WHO), who is keeping an eye on its spread. 

The above graph shows the proportion of cases that were down to AY.43 (yellow) and AY.4.2 (dark red). It also shows Delta (light green), Alpha (purple) and the old virus (dark green and pink). It reveals that the proportion of cases down to AY.4.2 and AY.43 has risen slightly over recent weeks

The graph above shows the percentage of cases that were down AY.43 (yellow), and AY.4.2(dark red). It also shows Alpha (purple), Delta (light green) and the old viruses (dark green, and pink). It shows that the proportion of cases below AY.4.2 has increased slightly in recent weeks.

AY.4.2 has spread to every local authority in England except five, data from the country's largest Covid surveillance centre reveals. The map shows prevalence for the fortnight ending October 23

AY.43 is only in some areas of the country, and appears to be focused around London and the South East. The map shows prevalence for the fortnight ending October 23

The maps above show the spread of both AY.4.2 (left), and AY.43(right). AY.4.2 has reached every English local authority, except five, according to data from the largest Covid surveillance center in the country. AY.43 appears to be limited to London and the South East, but is still present in certain areas of the country. Both maps show the prevalence for the week ending October 23rd.

The above graph shows the number of cases identified every week of Delta (green), Alpha (purple) the old virus (light pink and dark green), as well as Delta offshoots AY.4.2 (dark red) and AY.43 (yellow). It shows a drop in Delta but a slight rise among the subvariants

The graph below shows the number and severity of each week’s cases of Delta (purple), Alpha, and the old virus (light and dark pink), as well as the Delta offshoots AY.4.2 and AY.43. It shows a slight decrease in Delta, but a slight uptake among the subvariants.

AY.43 was first detected around July when Delta was taking off, and there is no evidence to suggest it is more infectious or better able to evade vaccines than other variants. It is behind more cases in Europe, especially France where it made up half of cases since September. In Germany it makes up a third, while in Denmark it makes up a fifth.

AY.43 first became apparent in July, as Delta was taking off. There is no evidence to suggest that it is more dangerous or more able to evade vaccines. It is responsible for more cases in Europe, particularly France, where it accounted for half of the cases since September. It is a third in Germany, and a fifth in Denmark.

There are approximately 100 AY lineages, which are offshoots or derivatives of the Delta variant. However, the vast majority are not worrying. 

AY.43 was first discovered in July as Delta was spreading throughout the globe. It is now much more common in Europe where it has been responsible for around half of all cases in France since September without triggering an increase in infections. 

AY.43: Everything You Need to Know 

Where did AY.43 get its name?

This subtype was first seen in the UK in July. 

The majority of its 84,000 cases were found in Europe, although scientists aren’t sure where it originated.

It is responsible for around half of all infections in France, two fifths it Belgium, one third in Germany, and about a fifth in Denmark.

Experts today said it was likely that it was imported from abroad. 

What mutations does this one have? 

AY.43 is a Delta subvariant, which means it has all of the mutations its ancestor had. This makes it highly infectious and better at escaping vaccinations than other strains.

What separates AY.43 from Delta is its N:Q9L mutation on the spike protein. Scientists are still not sure what impact this mutation has on the biology and behaviour of the virus. 

Why has it been highlighted? 

Experts are now noticing a growing number of mutant strains.

According to the most recent data from England’s largest Covid surveillance station, it was spotted 8,138 times.

982 cases were reported in the week ending October 23. This was slightly more than the 916 cases that occurred in the previous fortnight.

It was recently designated a subtype Delta because of the number of infections that have been detected. 

Should I be concerned by AY.43

Scientists today said that Britons didn’t need to worry about the spinoff AY.43 yet.

MailOnline was told by Professor Lawrence Young of Warwick Medical School that there was no reason for concern.

He added: ‘It seems to have been around for quite a long time and not taken off’. 

Experts expect a variant that has a significant evolutionary advantage will replace the other variants and become dominant. 

Globally, there have been 84,000 cases in 108 countries, with 7,000 in the US. Its true prevalence is likely to be much higher, as only a small percentage of samples are tested for variants and countries often do very little analysis. 

Professor Lawrence Young, a Warwick Medical School virologist, stated today that there is no need to be concerned about AY.43, and experts should “just keep an eye” on it. 

MailOnline was informed by him that the product had been around for a while and has not seen much success.  

The subtype was discovered for the first time on British shores during July, when the more transmissible Delta variation was sparking a wave in infections across the country.

It was found to be at low levels by genomic surveillance and it took approximately four months for it to begin competing with other strains.

AY.43 is the only known mutation N:Q9L. Scientists call this ‘unusual’ but have yet to find any evidence that it makes it more transmissible, or more able to evade vaccines. 

They claimed that the offshoot was likely imported from Europe to the UK, unlike the other Delta subvariant AY.4.2 which is believed have originated here. According to estimates, AY.43 is responsible for half of the cases in France, two-fifths in Belgium, and about a quarter in Germany.

Dr Jeffrey Barrett, who is the head of Covid surveillance at Sanger Institute, tweeted that ‘AY.43 may not be as widespread as AY.4.2 yet and is enriched only outside Greater London.

“This lineage is much more common in the UK, so these could be a variety introductions from abroad that have coincidentally increased a bit.

It has been growing in Germany, France, Belgium, Denmark and France. This could be a biological advantage or simply the fact that these countries are being hit with Delta case increase.

“[It]There are no spike mutations beyond Delta and only N:Q9L that appears to be unusual.

MailOnline spoke to Professor Young, who said that there is no need to be worried. He just recommends keeping an eye on the situation. Sublineages were always possible. The question is, why are we seeing any increase?

“Delta” seems to outcompete all others and still dominate. Its overwhelming transmissibility makes it impossible to destroy any other. [strains], and it just seems to dominate.

He said, “The virus spreads faster the more it is likely that it will change.” It is at high risk of generating variants.

“We have been facing problems in the last few months due to Delta. It is possible it will produce other variants, and that would be a disaster.

AY.43 was designated a subtype Delta because it had accounted to more than 80,000 global cases so far. The majority of these cases were in Europe.

There has been increased concern about the separate but identical offshoot AY.4.2. This was last week raised by health officials amid fears it may already have infected 150,000 Britons.

The UK Health Security Agency (UKHSA), who took over from the now-defunct Public Health England labeled the subtype as a ‘variant under examination’. 

Data from showed it was now behind about four per cent of cases in England, after rising from virtually none at the start of September

After rising from almost none at the beginning of September, data showed that it was now behind approximately four percent of England’s cases

In France it is now behind 60 per cent of cases after arriving in the country in August. But the country has seen its cases fall over the same period, suggesting the subtype is not much more transmissible than other strains

France: It now accounts for 60 percent of cases, after arriving in France in August. However, the country has seen its cases drop over the same time, suggesting that the subtype is not more transmissible than other strains.

In the United States, AY.43 is thought to be behind about two to three per cent of Covid infections

AY.43 is believed to be responsible for approximately two to three percent of all Covid infections in the United States.

And in Germany it is behind around 30 per cent of infections, although this proportion is now falling

It is responsible for around 30% of all infections in Germany, but this number is slowly falling.

This category is reserved to variants that are spreading in the UK and may be more transmissible, or better able evade vaccinations and other mutant strains. Mu, which was found in Colombia, is one of the other variants.

It is only one step away from a variant of concern’ label, which was already given to Alpha or Delta.

Scientists have suggested that AY.4.2 may be 10 to 15% more transmissible than its ancestor and will gradually replace the virus within the population over several months.

However, others at Northumbria University insist that the spread of the variant may be due to the “founder effect”, which is when a variant spreads because there is only one in a given area. 

AY.4.2 first appeared in the UK in late-June in London and South East England, before spreading to the rest.