Red-flag Covid symptom of Stratus and Nimbus variants and who is eligible for free vaccineCovid cases are rising thanks to new variants Nimbus and Stratus, but how can you tell if you have one of these strains? ‌XFG, dubbed Stratus, and NB.1.8.1, known as Nimbus, are now the most common variants being passed around in the UK. If you have a razor blade sore throat you could have one of these new variants. A hoarse voice or a "razor blade" sore throat is thought to be a tell-tale symptom of the latest types. ‌View 2 Images The new variants of Covid can cause a really sore throat.