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Data: The COVID Tracking Project, state health departments; Map: Andrew Witherspoon, Sara Wise, Naema Ahmed/Axios

Coronavirus cases are quickly spreading in Arizona, a handful of southern and western states and, ominously, Oklahoma — the planned site of President Trump's controversial rally this weekend.

Why it matters: Once community spread takes off, cases can begin to increase exponentially.

The big picture: “We’re at a point where there are warning signs going off, and people need to take steps to help control it," said Chris Meekins, a health policy research analyst at the investment bank Raymond James.

By the numbers: Oklahoma has seen a 91% jump in its coronavirus cases over the past week, and new cases are up 53% in Arizona.

Between the lines: Each week, Axios is documenting the change in new cases in each state. We use a seven-day average to minimize inconsistencies in when new cases are reported.

  • Overall, new coronavirus cases are up 11% nationwide over the past week.

New cases alone don't measure the extent of a state's outbreak, but many of these same states also are in worsening shape according to other measures.

  • Arizona, South Carolina, Louisiana, Oklahoma and Florida have seen significant growth in the percentage of coronavirus tests coming back positive over the last two weeks, according to Nephron Research, indicating that the case growth in these states isn't solely attributable to more testing.
  • Arizona, Texas, North Carolina and Alabama have also hit record hospitalizations in the last few days.
  • “For the first time, I would have to say, I’m growing worried about the system,” Donald Williamson, president of the Alabama Hospital Association, told the Alabama Political Reporter. He said that the Tuscaloosa area had only one ICU bed available Tuesday morning.

What we're watching: “Ultimately, the president doesn’t ask for permission before he” goes places, Oklahoma Gov. Kevin Stitt said yesterday, per Reuters. “So we found out that president was coming, so we are going to make sure it’s the best and as safe as possible.”

The bottom line: “People are going to want to react to really bad numbers," Harvard's Ashish Jha said. But "if you don’t slow the virus down, it'll keep going up, and exponential growth is a bad thing. Because it's building on itself.”

Go deeper

Coronavirus cases flat or growing in 48 states

Data: The COVID Tracking Project, state health departments; Map: Andrew Witherspoon, Sara Wise, Naema Ahmed, Danielle Alberti/Axios

The number of coronavirus cases increased in the vast majority of states over the last week, and decreased in only two states plus the District of Columbia.

Why it matters: This is a grim reminder that no part of the United States is safe from the virus. If states fail to contain their outbreaks, they could soon face exponential spread and overwhelmed health systems.

16 hours ago - Health

15 states broke single-day coronavirus records this week

Data: Compiled from state health departments by Axios; Map: Danielle Alberti/Axios

At least 15 states broke their single-day novel coronavirus infection records this week, according to state health department data reviewed by Axios.

The big picture: The number of coronavirus cases increased in the vast majority of states over the last week, and decreased in only two states plus the District of Columbia, Axios' Andrew Withershoop and Caitlin Owens report.

Coronavirus testing czar: "We are not flattening the curve right now"

Adm. Brett Giroir, the Health and Human Services official overseeing the nation's coronavirus testing efforts, told Congress Thursday that the U.S. is "not flattening the curve right now," and that the nationwide surge in new cases is not simply a result of more testing.

Why it matters: President Trump said at a press conference just hours earlier that the U.S. is getting the coronavirus "under control." He and other top members of his administration have sought to downplay the growing surge in infections as largely a product of increased testing.