Health officials are watching a new variant of Covid-19 which is being nicknamed 'Stealth Omicron'.

Potentially harder to detect and thought to be spreading more rapidly than the original Omicron strain which emerged late last year, the new relation BA.2 has now been designated a variant under investigation by the UK Health Security Agency.

With it now under the watchful eye of scientists, and England about to remove some of its final Plan B restrictions, we take a look at what virus experts are saying about it so far:

What is Omicron BA.2?

The original Omicron strain, or sub-lineage, which emerged late last year and led to a flurry of new winter restrictions across the globe is a variant known as BA.1 and is now the dominant strain in the UK accounting for the vast majority of the country's daily coronavirus cases.

As well as being more transmissible than Delta, the original Omicron BA.1 also has a unique identification tag thanks to its mutation, something known as the S gene drop out, which has made it easier to identify since its first outbreak using a straightforward PCR test without needing to find the variant using more time consuming, complicated and costly geonome sequencing.

The new and emerging BA.2 has been designated as a variant under investigation - one level below a variant of concern - because of an increasing number of cases both in the UK and around the world now being reported.
According to the World Health Organisation, while the original BA.1 Omicron variant remains the dominant strain, BA.2 is increasing in the UK alongside other countries including India, South Africa, Sweden, Singapore and Denmark and could even be outpacing the original strain now in some places.

In total, 40 countries worldwide have picked up more than 8,000 cases of BA.2 since the end of November last year but this strain is much harder to detect on a basic PCR test, meaning that this might not be the true picture.

While it is not possible, says the World Health Organisation, to determine where BA.2 has originated the first sequences were submitted from the Philippines while most samples have so far been uploaded from Denmark (currently 6,411 cases).

How many cases of BA.2 are there in the UK?

To date there have been 426 confirmed cases of BA.2.

But because this strain cannot be identified using a simple PCR test and can only be spotted using Whole Genome Sequencing - the actual number is likely to be a lot higher.

Only around a third of all positive cases found with a PCR are sent to be looked at more closely to see which coronavirus variant is responsible for the positive result. So while 400 sounds very low among the tens of thousands of cases reported each day, the reality is that there is likely to be many many more cases of BA.2 within communities that are going under the radar.

Scientists are not being able to further look at the genome sequencing behind every confirmed PCR result while recent changes to the testing guidelines - such as asymptomatic people being able to use a rapid lateral flow test at home instead of a PCR which means that their swab is not investigated at all, may also be in part responsible for the currently low number.

The earliest dated case was December 6 last year in the UK and the areas currently with the highest number of confirmed cases are in London - with 146 - and the South East with 97.

Why are scientists watching so closely?

Ever since coronavirus first emerged in March 2020 we have been told that variants would come and go, as is the case with any virus. Some - like Delta and Omicron - take off in huge numbers and alter the pace and path of the pandemic while others don't have the strength to knock the current dominant strain off its course and are only ever reported in low numbers.

But scientists remain alert to new variants or strains of Covid19 to ensure that any new mutations are spotted because there is always the risk that one may come along with the power to derail the vaccination programme and other protections we have in place.

The UKHSA says early analysis suggests that BA.2 compared to BA.1 does have 'an increased growth rate' but that further investigation is needed to find out what impact it has on someone's actual illness and that is taking place now.

While increased transmission has the potential to lead to greater disruption if growing numbers of people report sickness and isolation, just as we saw with Omicron's first wave which is thought to have now peaked, whether the new strain causes more serious illness is currently unclear.

But because BA.2 cannot be identified using a simple PCR test, unlike its relation BA.1, work must be done to ensure no large rise in cases or more serious illness is going undetected.

Dr Meera Chand, COVID-19 Incident Director at UKHSA, explained: "It is the nature of viruses to evolve and mutate, so it’s to be expected that we will continue to see new variants emerge as the pandemic goes on. Our continued genomic surveillance allows us to detect them and assess whether they are significant.

"So far, there is insufficient evidence to determine whether BA.2 causes more severe illness than Omicron BA.1, but data is limited and UKHSA continues to investigate."

Will England keep to Plan A?

Despite this new development England is continuing to move from Plan B to Plan A restrictions this week, which includes the axing of facemask as a legal requirement and the end of requests for people to work from home where they can.

Mandatory Covid certification is also about to come to an end.

But the government is quick to point out, that despite feeling like the chain between infection and very serious illness has been somewhat severed thanks to vaccines and high levels of immunity because of previous infection, cases remain high and people should continue to test regularly and take up vaccination appointments when they are offered.

Health and Social Care Secretary, Sajid Javid, said: "We are learning to live with this virus – and thanks to our world-leading surveillance system we can rapidly detect and carefully monitor any genetic changes to Covid19.

"Our exceptional vaccine rollout means the number of people severely affected by Covid19 is low, and the UK’s innovation and research has discovered life-saving treatments for those most at risk.

"As is routine for any new variants under investigation, UKHSA is carrying out laboratory and epidemiological investigations to better understand the characteristics of this variant. We will continue to monitor this situation closely and recommend appropriate public health measures if needed."