At the end of 2021, the Omicron variant displaced the Delta variant. Then, the Omicron BA.1 subvariant appeared; quickly followed by Omicron BA.2 in February 2022. Both are more contagious than Delta, with mostly mild clinical symptoms, as they escape more from part of our immunity.
For weeks now, the Omicron BA.2 subvariant has been replaced by Omicron BA.5 and, less so, by Omicron BA.4. Now we are at 50%: about half of the cases are due to Omicron BA.2 and the other half (and growing) are due mostly to Omicron BA.5.