By MEREDITH DELISO, ABC News

(WASHINGTON) — White House coronavirus response coordinator Dr. Deborah Birx is criticizing North Dakotans for having what she called the poorest mask use in the country, as the state experiences one of the highest rates of COVID-19 transmission nationwide.

Birx spent two days in the state this week as part of a nationwide tour that’s brought her to nearly 40 states during the coronavirus pandemic.

She told officials there that North Dakota had the worst mask use she had seen so far.

“Over the last 24 hours as we were here, and we were in your grocery stores, and in your restaurants and frankly even in your hotels, this is the least use of masks that we have seen in retail establishments of any place we have been,” Birx said Monday during a roundtable with local leaders and health officials in the state capital of Bismarck.

North Dakota is one of 16 states that don’t have a statewide mask mandate, according to Masks4All, a volunteer organization that advocates for more mask-wearing. Instead the governor has stressed personal responsibility, and mandates have been left up to individual mayors. In recent weeks, Fargo, Minot and Grand Forks have voted to implement a mask mandate, though Bismarck had not as of Tuesday evening.

Birx emphasized that mask-wearing is one of the main measures to limit the spread of COVID-19.

“There is not only evidence that masks work, there is evidence that masks utilized as a public health mitigation effort work,” said Birx, who noted that there is a “very high level” of COVID-19 in North Dakota.

“It doesn’t matter if you’re in a rural area, or if you’re in an urban area,” she said.

North Dakota currently has the highest number of daily COVID-19 cases per capita in the U.S., according to an analysis by the New York Times. In the most recent task force report, dated Oct. 18, the state also had the highest rate of cases in the country.

An ABC News analysis found that the daily rate of positivity and current hospitalizations in North Dakota have increased over the past two weeks.

On Tuesday, the state health department reported 896 new cases, for a daily positivity rate of 14.82%. The rolling 14-day positivity rate was 10.9% — more than double the rate that health experts recommend.

North Dakota saw a 39.9% increase in week-to-week new cases on Oct. 20, according to an Oct. 26 Health and Human Services memo obtained by ABC News. The state also surpassed 1,000 daily new cases for the first time on Oct. 20, the memo said. The state’s growing caseload has created a backlog, increasing the time it takes to notify people who have tested positive from 24 hours to 72 hours, according to HHS.

On the question of whether statewide mask mandates are effective, Birx said, “When you look at the states and when they implemented a mask mandate and you look at their cases per million and you look at their fatalities per million, they are lower than states that chose to recommend masks but not to mandate,” the Bismarck Tribune reported.

Birx did not say Monday whether she recommended that Gov. Doug Burgum mandate that masks be worn in public.

The Republican governor defended the state’s mask approach during Monday’s roundtable.

“We know we don’t have enforcement mechanisms in North Dakota where someone is going to force someone to wear a mask,” he said. “So again, it comes back to individuals choosing the role that they want to play in the community.”

Bismarck’s city commission was expected to vote on a mask order Tuesday night, local TV station KFYR-TV reported. The mayor has voiced opposition to a mandate in the city.

Birx did praise what she called North Dakota’s “superb” job of testing, while calling for all North Dakotans to practice social distancing and wear a mask, especially as the weather cools, to avoid what she called “silent spread” indoors.

“It starts with the community, and the community deciding that it’s important for their children to be in school, the community deciding that it’s important not to infect the nursing home staff who are caring for their residents — for North Dakotans — every day,” she said.

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