But numbers are growing both here and abroad, and the UK Health Security Agency named it a ‘variant under investigation’ on January 21.
Early analysis suggests it has a faster growth rate than the Omicron strain currently dominant in the UK, BA.1, but there is not enough evidence to say whether it causes more severe illness.
The Wellcome Sanger Institute analysed 38,000 positive Covid-19 tests taken in the week to January 15 to determine which variant they were.
It found one in 100 samples were now Stealth Omicron across England.
No cases of Steal Omicron were identified in the following parts of Yorkshire: Craven, Hambleton, Ryedale, Scarborough, Selby, Doncaster, Rotherham, Sheffield, Calderdale and Kirklees.
However, the sub-variant was detected in other parts of the region. Read on to find out more.
1. Harrogate
Four cases of 'stealth omicron' were found in Harrogate, with 104 total samples analysed in the week ending January 15. This means approximately four per cent of samples in Harrogate were found to be 'stealth omicron'.
2. Richmondshire
One case of 'stealth omicron' was found in Richmondshire, with 37 total samples analysed in the week ending January 15. This means approximately 3.2% of samples in Richmondshire were found to be 'stealth omicron'.
3. York
One case of 'stealth omicron' was found in York, with 126 total samples analysed in the week ending January 15. This means approximately 0.8% of samples in York were found to be 'stealth omicron'.
4. East Riding of Yorkshire
Two cases of 'stealth omicron' were found in the East Riding of Yorkshire, with 293 total samples analysed in the week ending January 15. This means approximately 0.7% of samples in East Riding were found to be 'stealth omicron'.