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HARRIS COUNTY, Texas (WJW/AP) — A Texas man is reportedly believed to be the first in the U.S. to die from the omicron variant of COVID-19.

Harris County Public Health announced Monday the man was between the ages of 50 and 60. The man was unvaccinated and had been infected with COVID-19 previously, according to a press release. He was at a higher risk of severe complications from COVID-19 due to his unvaccinated status and underlying health conditions.

“Our thoughts and prayers are with the patient’s family, and we extend our deepest sympathies,” Barbie Robinson, HCPH executive director, said in the release. “This is a reminder of the severity of COVID-19 and its variants. We urge all residents who qualify to get vaccinated and get their booster shot if they have not already.”

The omicron variant was first identified in South Africa in November 2021.

Omicron has raced ahead of other variants and is now the dominant version of the coronavirus in the U.S., accounting for 73% of new infections last week, federal health officials said Monday.

The Centers for Disease Control and Prevention numbers showed nearly a six-fold increase in omicron’s share of infections in only one week.

In much of the country, it’s even higher. Omicron is responsible for an estimated 90% or more of new infections in the New York area, the Southeast, the industrial Midwest and the Pacific Northwest. The national rate suggests that more than 650,000 omicron infections occurred in the U.S. last week.

Since the end of June, the delta variant had been the main version causing U.S. infections. As recently as the end of November, more than 99.5% of coronaviruses were delta, according to CDC data.

Much about the omicron variant remains unknown, including whether it causes more or less severe illness. Early studies suggest the vaccinated will need a booster shot for the best chance at preventing omicron infection but even without the extra dose, vaccination still should offer strong protection against severe illness and death.

“All of us have a date with omicron,” said Dr. Amesh Adalja, a senior scholar at the Johns Hopkins Center for Health Security. “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.”