Omicron Covid-19 variants BA.4 and BA.5 are on the rise in the U.S., adding two more highly contagious versions of the virus to the mix that has fueled a springtime surge in cases.
The closely related subvariants represented a combined 13% of U.S. cases for the week ended June 4, according to estimates the Centers for Disease Control and Prevention released on Tuesday. Evidence suggests the variants are yet-more contagious versions of Omicron, public-health experts said, that may be able to evade some of the immune protections people built up from infections triggered by another version of Omicron during the winter.
