The U.S. has reported its first death linked to Omicron now marking what is believed to be the second known death in the world associated with the COVID-19 variant.

The death was confirmed by Harris County Public Health in Texas. The deceased was a man between the ages of 50 and 60 who was unvaccinated and had been infected with COVID-19 previously. The man also had underlying health conditions.

The Centers for Disease Control and Prevention said on Monday that Omicron has become the dominant virus strain in the U.S., surpassing the Delta variant with 73.2% of cases of the virus making up the mutation over the last week.

Only two weeks earlier, 0.7% of COVID cases comprised the Omicron variant, according to data from the CDC.

Omicron was first detected in South Africa in late November. The CDC has warned that the variant is widespread and there is still much unknown about the new COVID strain. It was declared a variant of concern by the World Health Organization on Nov. 26.

Barbie Robinson, Harris County Public Health executive director, said of the death, “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.”

As reported by The Independent, Harris County Judge Lina Hidalgo said during a press conference on Monday that “Omicron is spreading incredibly quickly," adding, "First, we know that an increasing number of cases in Harris County are related to Omicron. It’s more transmissible. The amount of time it takes for the number of Omicron cases to double has been very worrisome.”

She continued by saying the CDC’s data indicated that Omicron doubles in two to three days, while Delta doubles every 11 days, the news outlet said.

Cases of Omicron have been detected in nearly every U.S. state and in at least 89 countries. Only Montana, North Dakota, South Dakota and Oklahoma have yet to confirm a case of Omicron, UPI reported.

The U.K. reported the first known death from the Omicron variant on Dec. 13.

Medical staff take care of a patient in the Covid-19 intensive care unit of the Robert Bosch hospital in Stuttgart
Medical staff takes care of a patient in the COVID-19 intensive care unit in the Robert Bosch Hospital in Stuttgart. AFP / THOMAS KIENZLE