CDC: Omicron Accounts for 90 Percent of COVID-19 Cases in Some Parts of US

Dr. Rochelle Walensky, the director of the Centers for Disease Control and Prevention, is seen in Washington in a file photograph. Greg Nash/Pool/Getty Images

The head of the Centers for Disease Control and Prevention (CDC) said the Omicron variant accounts for more than 90 percent of COVID-19 cases in some parts of the United States.

CDC director Dr. Rochelle Walensky said the variant makes up to 90 percent of infections in the South, Midwest, eastern Atlantic states, and northern Pacific states.

“This rapid increase in the proportion of Omicron circulating around the country is similar to what we’ve seen across the world,” she said in a White House COVID-19 press briefing. Earlier this week, the CDC found that Omicron made up about 73 percent of all cases in the United States last week, up significantly from the previous week.

Several recent studies, including one conducted by Scottish officials, found that the hospitalization rate is a fraction of that seen during the Delta wave. They found that if Omciron acted in the same manner as Delta, they would expect about 47 hospitalizations nationwide. There are currently only 15, researchers found.

And a leaked study from the UK Health Security Agency found that individuals who contract Omicron are less likely to become severely ill compared with those who contract Delta. An analysis of the variant by Imperial College London (pdf) also found that Omicron’s mutations may have made it a milder strain than Delta.

Despite the encouraging signs, some officials have indicated that Omicron still presents a threat.

World Health Organization technical lead Dr. Maria van Kerkhove, for example, told reporters this week that the health body doesn’t have enough information yet to draw a conclusion that the variant is milder.

“We have not seen this variant circulate long enough in populations around the world, certainly in vulnerable populations,” she said, according to the Reuters news agency. “We have been asking countries to be cautious, and to really think, especially as these holidays are coming up.”

Omicron was first detected last month in southern Africa and Hong Kong. Preliminary data indicated it was more resistant to vaccines developed before it emerged.

A study from South Africa’s National Institute for Communicable Diseases (NICD) also suggested that those infected with Omicron were much less likely to end up in the hospital than those with the Delta strain. COVID-19 cases also appear to have peaked in South Africa’s Gauteng province, where Omicron first emerged, it said.

The study, which has not been peer-reviewed, compared South African Omicron data from October and November with data about Delta between April and November.

“In South Africa, this is the epidemiology: Omicron is behaving in a way that is less severe,” the NICD’s Professor Cheryl Cohen said. “Compellingly, together our data really suggest a positive story of a reduced severity of Omicron compared to other variants.”

Reuters contributed to this report.