Rapid infection rate of omicron Covid variant is causing concern, as UK braces for 1 million cases

LONDON — The rise of omicron Covid cases in the U.K. is on such steep trajectory that the country has been told to brace for one million cases by the end of the month.

The UK Health Security Agency said Wednesday that omicron is displaying a significant growth advantage over the delta variant, “meaning that it is likely to outcompete delta in the U.K. and become the dominant variant.”

This assessment is based on analysis of U.K. data showing increased household transmission risk, increased secondary attack rates (the chance of each...