The highly contagious coronavirus strain BA.2 is now responsible for more than four in five infections across England, research shows.
Researchers analysing positive Covid tests from the week to 12 March found 84 per cent were the subvariant, branded ‘Stealth Omicron’.
That is up from 74 per cent the week before.
The analysis by the Wellcome Sanger Institute comes as coronavirus infections and hospitalisations surge across the UK, with researchers saying the contagious subvariant is a key reason for the spike.
The situation in Hampshire for the percentage of positive cases that were Stealth Omicron is:
Hart – 88 per cent
Rushmoor – 87.5 per cent
Gosport – 87.1 per cent
Basingstoke and Deane – 86.2 per cent
East Hampshire – 82.3 per cent
Winchester – 82.2 per cent
New Forest – 81.2 per cent
Eastleigh – 81.1 per cent
Fareham – 80.8 per cent
Havant – 80.3 per cent
Isle of Wight – 78.5 per cent
Portsmouth – 76.3 per cent
Test Valley – 75.9 per cent
Southampton – 72.3 per cent
Stealth Omicron got its nickname because it is more difficult to differentiate from Delta than the original Omicron variant, BA.1.
It is also more contagious but early studies seem to show no greater risk of hospitalisation for an infected person, according to the UK Health Security Agency (UKHSA).
Cases in Portsmouth have continuously climbed since so-called ‘Freedom Day’ on February 24, when coronavirus laws ended.
On February 24 there were 76 new positive tests, with a seven-day average of 97.6 new cases. That is tests taken on February 24.
On March 17 – the most recent date for which comparable figures are available – there were 350 positive tests, with a seven-day average of 333.3 new cases.
A spokesperson for the UKHSA said: ‘Omicron BA.2 is now the dominant variant in the UK, and has a significant growth advantage over Omicron BA.1.
‘UKHSA continues to monitor all available data related to Covid-19 variants as a matter of routine, both in the UK and internationally.
‘Vaccination provides a high level of protection against severe illness and it's important that everyone has had their latest dose.
‘We can all help reduce transmission by wearing a face covering in crowded or enclosed spaces, washing hands regularly and keeping rooms well ventilated.’
The Wellcome Sanger Institute analysed more than 41,000 Covid tests from the week ending March 12, taken from every part of England.
Regionally, London had the greatest proportion of samples testing positive for Stealth Omicron.
The region had 87.9 per cent of samples testing positive, followed by the East of England with 85.6 per cent and the North West with 85.1 per cent.
The North East had the lowest positivity rate in England with 71.7 per cent of samples testing positive for Stealth Omicron.
At a local level South Bucks had the greatest proportion of tests coming back positive.
The authority had a positivity rate of 97 per cent, followed by Rossendale which recorded 96.3 per cent and Barrow-in-Furness with 95.9 per cent.