Coronavirus updates: Birx warns of 'very different' spread of COVID-19

An ABC News analysis of COVID-19 trends across all 50 U.S. states as well as Washington, D.C. and Puerto Rico found there were increases in newly confirmed cases over the past two weeks in 28 states.

The analysis also found increases in the daily positivity rate of COVID-19 tests in 25 states, increases in COVID-19 hospitalizations in 35 states and increases in daily COVID-19 death tolls in 18 states plus Puerto Rico.

The seven-day average of new cases in the United States has now surpassed 44,000, the highest it has been since Aug. 21.

Two states -- Montana and South Dakota -- reported their highest single-day increases in the number of new COVID-19 cases. Seven states -- Arkansas, Iowa, Montana, Oklahoma, South Dakota, Wisconsin and Wyoming -- hit a record number of current COVID-19 hospitalizations in a day.

Although figures in the Northeast still remain relatively low, the number of new cases continues to slowly increase, relative to the figures that were seen during the spring. The region's seven-day average of new cases is now the highest it has been since June 2. In the last month alone, that average has increased by more than 69%.

In the Midwest, the number of new cases continues to hit record levels, averaging 13,200 cases per day, largely driven by consistently high caseloads in Montana, North Dakota, South Dakota and Wisconsin. The number of current COVID-19 hospitalizations in many midwestern states also continues to climb. Since Sunday, current hospitalizations in Montana, Nebraska, North Dakota, Oklahoma, South Dakota and Wisconsin have all hit record highs.

The number of new cases in the South remain significantly lower than they were throughout the summer. However, the South still contributes to more than 45% of the country's daily regional caseload, with an average of over 18,000 new cases per day.

Over the past three weeks, the number of new cases in the West has increased by 26%. Idaho and Utah still continue to produce high daily case totals. Although the figures in California are on a downward trend, the state continues to report a high number of new cases every day.

The trends were all analyzed from data collected and published by the COVID Tracking Project over the past two weeks, using the linear regression trend line of the seven-day moving average.

ABC News' Benjamin Bell, Brian Hartman, Soorin Kim and Arielle Mitropolous contributed to this report.

Dr. Deborah Birx, the White House coronavirus response coordinator, said states in the Northeast are showing "troubling signs" that they could reemerge as COVID-19 hotspots.

"It’s early here," Birx said at a press conference Thursday, after participating in a roundtable discussion at the University of Connecticut's campus in Hartford. "We can continue in the Northeast to contain the virus."

As the weather turns colder, Birx said the novel coronavirus is transmitting more rapidly within families and social groups than in schools or workplaces where people are taking precautions. She said it's a lesson that was learned in the South during the summer when people went indoors for air-conditioning to escape the heat and humidity.

"What we’re seeing in the community is much more spread occurring in households and in social occasions, small gatherings where people have come inside, taken off their mask to eat or drink or socialize with one another," she said.

Northeastern states, once a hotbed for the virus, are beginning to see upticks in COVID-19, case numbers, positivity rates and hospitalizations.

"This is really a message to everyone in Connecticut: the kind of spread that we’re seeing now is very different from the spread we experienced in March and April,” Birx warned. "What we did in the spring is not going to work in the fall."