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.
9. Bradford
Two cases of 'stealth omicron' were found in Bradford, with 776 total samples analysed in the week ending January 15. This means approximately 0.3% of samples in Bradford were found to be 'stealth omicron'.