The latest estimate by the US Centers for Disease Control and Prevention shows that more than 60 percent of new COVID-19 cases in the country are caused by the Omicron XBB.1.5 subvariant.

The CDC estimates that the fast-spreading strain accounted for 66.4 percent of the country's coronavirus cases for the week through Saturday.

That is an increase of more than 10 percentage points from the previous week's figure of 55.9 percent.

The average daily number of new coronavirus infections reported in the US was about 40,000 as of Wednesday, marking a fourth straight weekly decline. The figure does not include positive cases identified by self-testing kits.

The average daily number of COVID-19 hospital admissions as of Tuesday was about 3,900, and the average daily number of deaths as of Wednesday was about 490. These figures have been on a downward trend since mid-January.

Regarding XBB.1.5, the World Health Organization says no early signals of increased severity have been observed. But it points out that the subvariant may cause infections to rise globally.