An Omicron subvariant of the coronavirus has been spreading rapidly in the United States.

The US Centers for Disease Control and Prevention said on Friday that 27.6 percent of all new infections in the country during the week through January 7 are projected to be the XBB.1.5 subvariant.

While all other Omicron lineages have been on the decline since late December, XBB.1.5 cases have jumped over a one-month period from an estimated 2.3 percent of new cases as of December 3. In a region including the eastern state of New York, it is estimated to account for more than 70 percent of new infections.

White House COVID-19 Response Coordinator Ashish Jha tweeted on Wednesday that the subvariant may be more inherently contagious. He called on people to take basic precautions such as getting booster shots and wearing masks in crowded indoor spaces.

In the US, a daily average of 6,500 people were newly admitted to hospitals as of January 4, up around 30 percent from one month before. However, the number of deaths per day has mostly stayed below the 400 mark since the middle of last October.