Over half of people infected with the omicron variant didn't know it, a study finds

The majority of people likely infected with the omicron variant that causes COVID-19 were not aware they contracted the virus, which likely played a role in the rapid spread of omicron, according to a study published this week.

Researchers at Cedars-Sinai, a nonprofit health organization based in Los Angeles, examined the infectious status of individuals during the omicron surge in the U.S.

Omicron was first detected in November 2021 and has become the most dominant strain of COVID-19. Common symptoms are typically less severe than other variants and include cough, headache, fatigue, sore throat and a runny nose, according to the researchers.

What did researchers find?

The study analyzed 2,479 blood samples from adult employees and patients at Cedars-Sinai Medical Center around the time of the omicron variant surge.

Of the 210 people who likely contracted the omicron variant — based on antibodies in their blood — 56% percent did not know they had the virus, the researchers found.

They also found that only 10% of those who were unaware reported having any symptoms relating to a common cold or other type of infection.

"We hope people will read these findings and think, 'I was just at a gathering where someone tested positive,' or, 'I just started to feel a little under the weather. Maybe I should get a quick test,'" said Dr. Susan Cheng, one of the authors of the study.

"The better we understand our own risks, the better we will be at protecting the health of the public as well as ourselves," said Cheng, who directs the Institute for Research on Healthy Aging in the Department of Cardiology at Cedars-Sinai's Smidt Heart Institute.

The findings help us understand how omicron spreads

A lack of awareness could be a major factor in the rapid transmission of the virus between individuals, according to the study.

"Our study findings add to evidence that undiagnosed infections can increase transmission of the virus," said Dr. Sandy Y. Joung, first author of the study who serves as an investigator at Cedars-Sinai.

"A low level of infection awareness has likely contributed to the fast spread of Omicron," Young said.

Although awareness among health care employees was slightly higher, the researchers said it remained low overall.

Researchers say further studies are needed, "involving larger numbers of people from diverse ethnicities and communities ... to learn what specific factors are associated with a lack of infection awareness," according to the news release.