The total number of COVID-19 cases in the United States topped 50 million on Monday, according to data from Johns Hopkins University, as the Delta variant continues to threaten Americans and the newly discovered Omicron variant spreads.

U.S. COVID-19 case count rose to 50,009,507, with a total of some 800,000 deaths, as of 2:22 p.m. local time (1922 GMT), showed the data.

California topped the state-level caseload list, with 5,169,348 cases. Texas confirmed the second most cases of 4,394,772, followed by Florida with 3,754,042 cases, New York with 2,854,057 cases, and Illinois with more than 1.9 million cases, according to the tally.

States in colder parts of the country, such as Vermont, New Hampshire and Michigan, are seeing the biggest surge in new infections on a per capita basis.

The number of hospitalized COVID patients is rising as well, up 20 percent since the Thanksgiving holiday at the end of November. 

The United States remains the nation worst hit by the pandemic, with the world's most cases and deaths, making up more than 18 percent of the global caseload and more than 15 percent of the global deaths.

U.S. COVID-19 infections among children 'extremely high' 

COVID-19 infections among children are "extremely high" in the United States during the past two weeks, warned the latest report published by the American Academy of Pediatrics.

"Over 164,000 child cases were added the past week, an increase of nearly 24 percent over the prior week," said the report. As of December 9, nearly 7.2 million children have tested positive for COVID-19 since the onset of the pandemic, it added.

For the week ending Thursday, the number of child cases covered 23.6 percent of reported weekly COVID-19 cases, adding that children aged under 18, make up 22.2 percent of the U.S. population.

Getting vaccinated still the priority

More states in the United States are reporting Omicron cases, with some 75 known cases in 30 states, though the Delta variant still account for 99 percent of new cases, according to CBS News.

In response, health officials are calling on people to get vaccinated and the U.S. Centers for Disease Control and Prevention strengthened its recommendations for booster shots in November. 

Getting vaccinated should still be the priority for Americans but having pills that can keep people out of the hospital "could be a lifesaver," said U.S. Secretary of Health and Human Services Xavier Becerra.

Now some 76 percent of eligible people have received at least one vaccine dose in the U.S., and 65 percent has been fully vaccinated, WebMD reported on Monday. While a total of 14 percent of Americans have now received a booster shot, according to Reuters.

An analysis of Reuters data shows it took almost a year to reach first 25 million COVID cases and 323 days, less than a year to go from 25 million to 50 million cases.

(With input from agencies)