The strain, officially named AY.4.2, spreads more easily than other variants and now accounts for more than half of analysed cases in one part of the country: the Torridge area of Devon.
Officials designated the strain a ‘variant under investigation’ on October 20.
Scientists are still working out whether it is more transmissible or whether there are other factors helping it to spread.
Vaccines are proving as effective against Delta Plus as they are against other Delta variants, two separate studies have found.
And there is “no evidence of increased severity based on risk of hospitalisation or death”, the UK Health Security Agency (UKHSA) has said.
Preliminary findings from the Wellcome Sanger Institute, one of the research bodies that works with the UKHSA, show potential hotspots for the variant.
It analysed more than 36,000 positive Covid-19 tests from the week to November 13.
Torridge in Devon was found to have the highest proportion of Delta Plus cases, at 50.3%, followed by Mid-Devon at 38.1%.
The research is provisional, but gives more localised detail than the official figures published by the UK Health Security Agency.
The number of tests analysed varies for each area, so the figures are given to give context to the findings:
Worthing was ranked the third highest in England, with 37.5% of the samples tested being confirmed as Delta Plus. However the number of samples tested were relatively small - just 24 tests, of which nine were found to be Delta Plus.
Next was Arun which was ranked 71 in England with 18 out of 99 tests analysed confirmed as Delta Plus - a result of 18%.
Mid Sussex had 30 samples analysed, with five confirmed as Delta Plus, giving a result of 16%. It was ranked 92 in England.
Adur was listed as 117th in England with a Delta Plus rate of 15.6% - five of 32 tests looked at for the study.
Chichester had 60 tests analysed, eight of which were confirmed at Delta Plus, or 13%, giving in a ranking of 154 nationwide.
Horsham ranked 173rd in England, with four out of 32 tests showing up as the variant, 12%.
Crawley had just seven tests analysed, one of which was Delta Plus. Because the sample size was so small it has not given a national ranking.