A “STEALTH” version of the coronavirus Omicron variant which can’t be identified with standard tests has been found, scientists say.

The new version of the variant was identified in recent days in South Africa, Australia and Canada, The Guardian reports, but there are concerns that the difficulties in detecting it may mean it has spread further afield.

So far, none of the “stealth” variant cases have been found in Scotland or the UK as a whole.

This “stealth” variant has a number of mutations making it similar to the initial Omicron variant but it does not have one genetic change (so-called S-Gene drop-out) that helps PCR tests to flag it as a possible case.

Professor Francois Balloux of the University College London Genetics Institute explained that there are “two lineages within Omicron, BA.1 and BA.2, that are quite differentiated genetically”.

BA.2 may behave differently than the initial Omicron, she added. Another researcher added that the “stealth” version is genetically distinct enough that it may be classed as an entirely new “variant of concern” if it spreads quickly.

READ MORE: Nicola Sturgeon confirms ten-fold spike in Omicron cases in Scotland

Scientists are fearful that the stealth version could spread unnoticed while public health chiefs focus on identifying and isolating standard Omicron cases.

Meanwhile on Tuesday Nicola Sturgeon said around 4% of Covid-19 cases in Scotland are likely to be the original Omicron variant.

Scotland’s First Minister said the “really concerning development” from the latest variant meant all current restrictions would remain in the country and further measures such as an extension to vaccine passports could not be ruled out.

Contact tracing will now be enhanced in Scotland, with household contacts of close contacts of positive cases told to test and isolate.

She told employers that if they had staff working from home at the start of the pandemic they should enable them to do so again until the middle of January.

Speaking in the Scottish Parliament, Sturgeon said there has been more than a tenfold increase in Omicron cases over the last week.

A total of 28 new cases were recorded in the past 24 hours, taking the overall number to 99.