Omicron now dominant coronavirus strain in new U.S. cases


The Omicron variant accounted for 73 percent of new coronavirus cases between Dec. 12 and 18, the Centers for Disease Control and Prevention said on Monday.
The Delta variant has been the driving force in U.S. infections for more than five months, with CDC data showing that at the end of last month, more than 99.5 percent of coronavirus cases were Delta. Omicron was first detected in southern Africa in late November, and has since been found in 90 countries. It's estimated that last week, more than 650,000 Omicron infections were reported in the United States.
In New York, the Pacific Northwest, and the Southeast, it's believed that at least 90 percent of new infections are because of Omicron, The Associated Press reports. The numbers are "stark," CDC Director Dr. Rochelle Walensky said, but "they're not surprising," as they follow the growth seen in other countries. She also anticipates that over time, "Delta will be crowded out by Omicron."
Subscribe to The Week
Escape your echo chamber. Get the facts behind the news, plus analysis from multiple perspectives.

Sign up for The Week's Free Newsletters
From our morning news briefing to a weekly Good News Newsletter, get the best of The Week delivered directly to your inbox.
From our morning news briefing to a weekly Good News Newsletter, get the best of The Week delivered directly to your inbox.
Researchers are still trying to determine if Omicron causes a more severe illness; both Moderna and Pfizer have said in lab tests, a third dose of their COVID-19 vaccines increased immune response against Omicron. Dr. Amesh Adalja, a senior scholar at the Johns Hopkins Center for Health Security, told AP he expects Omicron will further spread during the holidays.
"All of us have a date with Omicron," Adalja said. "If you're going to interact with society, if you're going to have any type of life, Omicron will be something you encounter, and the best way you can encounter this is to be fully vaccinated."
Sign up for Today's Best Articles in your inbox
A free daily email with the biggest news stories of the day – and the best features from TheWeek.com
Catherine Garcia has worked as a senior writer at The Week since 2014. Her writing and reporting have appeared in Entertainment Weekly, The New York Times, Wirecutter, NBC News and "The Book of Jezebel," among others. She's a graduate of the University of Redlands and the Columbia University Graduate School of Journalism.
-
Today's political cartoons - April 19, 2025
Cartoons Saturday's cartoons - free trade, judicial pushback, and more
By The Week US
-
5 educational cartoons about the Harvard pushback
Cartoons Artists take on academic freedom, institutional resistance, and more
By The Week US
-
One-pan black chickpeas with baharat and orange recipe
The Week Recommends This one-pan dish offers bold flavours, low effort and minimum clean up
By The Week UK
-
Hantavirus: the rare pathogen linked to rodents that attacks the lungs
The Explainer Despite the low risk of contracting it, the virus could be potentially deadly
By Theara Coleman, The Week US
-
The sneaking rise of whooping cough
Under the Radar The measles outbreak isn't the only one to worry about
By Theara Coleman, The Week US
-
RFK Jr. visits Texas as 2nd child dies from measles
Speed Read An outbreak of the vaccine-preventable disease continues to grow following a decade of no recorded US measles deaths
By Peter Weber, The Week US
-
What does Health and Human Services do?
The Explainer Cuts will 'dramatically alter' public health in America
By Joel Mathis, The Week US
-
Shingles vaccine cuts dementia risk, study finds
Speed Read Getting vaccinated appears to significantly reduce the chances of developing Alzheimer's and other forms of dementia
By Peter Weber, The Week US
-
Tuberculosis sees a resurgence and is only going to get worse
Under the radar The spread of the deadly infection is buoyed by global unrest
By Devika Rao, The Week US
-
Measles outbreak spreads, as does RFK Jr.'s influence
Speed Read The outbreak centered in Texas has grown to at least three states and Health Secretary Robert F. Kennedy Jr. is promoting unproven treatments
By Peter Weber, The Week US
-
MAHA moms: the cohort of women backing RFK Jr.'s health agenda
The Explainer America's head health honcho has a flock of supporters spreading the MAHA message on social media
By Theara Coleman, The Week US