Is Omicron Driving a Winter COVID Surge?

The U.S. is going through yet another COVID-19 surge. After a summer lull, cases spiked in early September before lowering just before Halloween. And now, they’re on a massive uptick.

As of December 17, there were 156,754 new COVID-19 cases reported in the country—a dramatic increase from the 120,337 new cases reported on November 30. The sharp jump in cases partially coincides with the discovery of the highly contagious Omicron variant in the U.S.

Omicron, which was named a variant of concern by the World Health Organization (WHO) on November 26, has now been detected in all but five U.S. states.

The Delta variant, which has been behind the majority of COVID-19 cases in the U.S. for months, is still the dominant strain of the virus in the country. But data show that Omicron is already causing nearly 3% of COVID-19 cases in the U.S., suggesting it’s quickly making headway.

Is Omicron to blame for the recent surge in cases? It might be too soon to know.

“In recent weeks, infections have increased steeply, coinciding with the detection of [Omicron],” the WHO said in a statement on November 26. Since then, Omicron cases have shown up around the world and have been linked to several surges.

The WHO cited research that found Omicron has several mutations in its spike protein, which is what the virus uses to infect cells. The variant also comes with an increased risk of reinfection in people who have previously had COVID-19 and is spreading quickly.

“This variant has been detected at faster rates than previous surges in infection, suggesting that this variant may have a growth advantage,” the WHO said.

What Does the Data Say About Omicron?

A recent report from the Centers for Disease Control and Prevention (CDC) analyzed data from 43 Omicron cases detected in the U.S. between December 1 and December 8.

Researchers found that 58% of the cases were in people between the ages of 18 and 39 and that 14 of the COVID-19 patients had traveled internationally within 14 days before they either developed symptoms or tested positive for the virus.

The data show that 79% of the cases (or 34) happened in people who had finished their primary series of the COVID-19 vaccine. Researchers found that 14 people had gotten their booster vaccine, and five of those received their booster dose less than 14 days before they developed symptoms. Six patients had a previously documented case of COVID-19. One patient was hospitalized for two days.

According to the WHO and CDC data, Omicron symptoms have been “mild” so far.

However, they’ve largely been in people who are vaccinated or younger people who typically have less severe symptoms, Thomas Russo, MD, professor and chief of infectious disease at the University at Buffalo in New York, told Verywell.

“Initial reported infections were among university students—younger individuals who tend to have more mild disease—but understanding the level of severity of the Omicron variant will take days to several weeks,” the WHO said.

Is Omicron Behind the Most Recent Surge?

Experts say it’s too early to tell if Omicron is fueling the current winter surge, given that the Delta variant is still responsible for the majority of COVID-19 cases in the country. There are also other factors beyond Omicron at play.

“It depends upon what part of the country you are in,” Amesh A. Adalja, MD, infectious disease expert and senior scholar at the Johns Hopkins Center for Health Security, told Verywell. “I suspect that some of the surge in places like New York City is driven by Omicron but other parts of the country may still be dealing with Delta primarily. Delta still is predominating but it will likely be overtaken soon.”

Russo said the current surge is being fueled “by both Delta and Omicron.” Still, he added, “there’s a lot more Omicron than we appreciate that is driving cases, although Delta is still problematic.”

Omicron “is obviously spreading around the world extraordinarily quickly—in the U.K., it's doubling every 2.5 days,” Russo said.

According to the WHO, documented Omicron cases are doubling every 1.5 to three days.

Richard Watkins, MD, an infectious disease physician and professor of internal medicine at the Northeast Ohio Medical University, told Verywell that Omicron is “spreading like wildfire” and predicts that it “will likely be the majority of cases by January.”

Adalja said that lifestyle factors play a role, too. He specifically cites "pandemic fatigue coupled with colder weather driving people indoors” as contributing to the spread of the virus.

Watkins agreed. “People are becoming too lax with mask-wearing in public,” he said. “Even if you are vaccinated, you can still get infected and spread the virus.”

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