The ‘Delta Plus’ COVID variant: What is it and should we be concerned?

A super closeup of COVID, which continues to mutate into different variants like 'Delta Plus'.
A super closeup of COVID, which continues to mutate into different variants like 'Delta Plus'. Copyright Shutter2u / Canva
By Amber Bryce with AP
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A relative of the Delta variant is under investigation in the UK and there’s concern over potential increased transmissibility.


A new ‘Delta Plus’ variant of COVID-19 could spread more easily than the original Delta, and is currently under investigation in the UK.

The Delta variant accounts for most cases in the UK, but new official data reports that 6 per cent of analysed COVID-19 cases are AY.4.2, also known by some as ‘Delta Plus’.

There is currently no evidence that AY.4.2 causes people to become more unwell.

The subvariant has been elevated to a ‘variant under investigation’, which means it is “considered to have concerning epidemiological, immunological or pathogenic properties”, according to

It is important to note that AY.4.2 is not yet a ‘variant of concern’, the highest risk category, and experts are confident that COVID vaccines will continue to protect people against it.

“[Delta remains] by far the most dominant variant in terms of global circulation” said Maria Van Kerkhove, the World Health Organisation’s technical lead on COVID-19, at a public session this week.

“Delta is dominant, but delta is evolving,” she said, adding that the more the virus circulates, the greater chances it has to mutate.

What is ‘Delta Plus’?

Viruses are always mutating, spawning minor variations that are more effective at spreading infection.

This particular variant - AY.4.2 - has two mutations in the spike protein, which helps the coronavirus invade the body’s cells.

Preliminary evidence suggests that this subvariant could be 10-15 per cent more transmissible than the original Delta, but more evidence is needed to fully understand its risk and whether it is responsible for causing an increase in UK cases.

Speaking to the BBC, Professor Francois Balloux, director of University College London's Genetics Institute, said: "It is potentially a marginally more infectious strain. It's nothing compared with what we saw with Alpha and Delta, which were something like 50 to 60 percent more transmissible. So we are talking about something quite subtle here and that is currently under investigation."

One to watch

The United Nations’ health agency is currently tracking 20 variations of the delta variant. The AY.4.2 is “one to watch because we have to continuously keep an eye on how this virus is changing,” said Van Kerkhove.

Outside of the UK, there have been few cases of AY.4.2.

In the US, the delta variant accounts for nearly all COVID-19 cases. The newer “delta plus” variant has been spotted “on occasion,” but it’s not yet a concern, health officials in the US said.

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