The United States has marked what is believed to be the first death related to the omicron COVID-19 variant.

Texas’ Harris County reports the man, in his 50s, was unvaccinated with a previous Covid infection and underlying health problems that put him at high risk of severe complications.

Harris County Judge Lina Hidalgo tweeted about the man’s death.

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.

Less that a month ago, the Delta variant was responsible for more than 99 percent of new cases.