Washington DC: The United States has entered a "new phase" of the pandemic, White House coronavirus advisor Deborah Birx warned Sunday, with rural areas just as threatened as major cities.

Birx, who heads the White House coronavirus task force, told CNN's "State of the Union" that local virus mitigation procedures were starting to work, but added that "what we are seeing today is different from March and April".

"It is extraordinarily widespread. It's into the rural as equal urban areas," she added. "To everybody who lives in a rural area, you are not immune or protected from this virus."

"We are in a new phase," Birx said.

She added that sticking to health and safety guidelines -- such as wearing a mask, maintaining personal hygiene and observing social distancing -- was crucial.

She said people living in multigenerational households in an area that is experiencing an outbreak should wear masks inside the home to protect the elderly or those with underlying conditions.

Alaska, Hawaii, Missouri, Montana and Oklahoma are among the states witnessing the largest surge of infections over the past week, according to a Washington Post analysis of health data. Experts also see worrisome trends emerging in major East Coast and Midwest cities, and anticipate major outbreaks in college towns as classes resume this month.

If people wear masks and avoid crowds, Giroir said, it gives the same outcome as a complete shutdown.

"That's why we're going to all the states, we're on local radio, we give specific instructions to every governor by county, what they need to do when we start – when those counties start tipping yellow, because that's the time when you have to stamp it down," he said.

As of Sunday, the US had tallied more than 4,665,000 cases of COVID-19 and 154,834 deaths, according to Johns Hopkins University, making it by far the hardest-hit country in the world.

The US notched 47,508 new cases on Sunday -- a slight dip from the previous five days, which had all recorded more than 60,000 new infections.