Amid a rise in the detection of cases of the Omicron variant of the coronavirus in the United States, health experts are urging people to get vaccinated and get boosters. (Photo: Getty Images)   

The United States crossed 50 million coronavirus cases on Sunday, according to Reuters tally, as the Delta variant continues to threaten Americans and the newly discovered Omicron variant spreads.

After about two months of declining infections, the United States has reported daily increases for the past two weeks, driven by the more easily transmitted Delta variant.

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

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

Over the past month, deaths have increased by 4.6%, with the country's death toll surpassed 800,000.

Nearly half of US states have detected cases of the Omicron variant, but the Delta variant still accounts for 99% of current COVID cases, CDC Director Dr. Rochelle Walensky has said.

For Omicron to be a significant problem, it will need to change that balance to become dominant. "If we suddenly start to see 10% of new infections being Omicron, and then it goes up the next week to 20%, that would tell us that we're in a replacement wave such as we saw when Delta replaced Alpha," said John Moore, a professor of microbiology and immunology at Weill Cornell Medical College.

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.

Laboratory studies released this week suggest that the Omicron variant of the coronavirus will blunt the power of Pfizer and BioNTech's vaccine to prevent COVID-19 infection after two doses, although a third dose may restore that protection.

Around 14% of people in the United states, have now received a booster shot. Close to 10 million of those people have gotten the extra shots since the Thanksgiving holiday, with concerns about the Omicron variant.

Pfizer Inc and Merck have developed COVID-19 antiviral drugs that work across all variants, with countries rushing to buy the pills.

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 US Secretary of Health and Human Services Xavier Becerra.

Reuters