Researchers fear new Covid variant could spread unnoticed because rough means of flagging up cases does not work
Scientists have identified a “stealth” version of the Omicron variant which cannot be detected with the routine tests that public health officials are using to track its spread around the world.
The stealth variant has many mutations in common with standard Omicron, but it lacks a particular genetic change that allows lab-based PCR tests to be used as a rough and ready means of flagging up probable cases.