A dark horse variant of COVID-19 seems to be overtaking all the others and leading to a gradual rise in cases and hospitalizations this winter.
The excitement and build up to the holidays also led to an increase in COVID-19 cases the last two weeks of December due to the fast-moving subvariant XBB 1.5.
Cases jumped from just over 20% to a little over 40% across the U.S. from the middle of December to the end.