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.
5. Leeds
Four cases of 'stealth omicron' were found in Leeds, with 937 total samples analysed in the week ending January 15. This means approximately 0.4% of samples in Leeds were found to be 'stealth omicron'.
6. Barnsley
One case of 'stealth omicron' was found in Barnsley, with 276 total samples analysed in the week ending January 15. This means approximately 0.4% of samples in Barnsley were found to be 'stealth omicron'.
7. Hull
One case of 'stealth omicron' was found in Hull, with 316 total samples analysed in the week ending January 15. This means approximately 0.3% of samples in Hull were found to be 'stealth omicron'.
8. Wakefield
One case of 'stealth omicron' was found in Wakefield, with 361 total samples analysed in the week ending January 15. This means approximately 0.3% of samples in Wakefield were found to be 'stealth omicron'.