Arizona, Florida, California and Nevada report record-high single-day increases in coronavirus cases

• The Arizona Department of Health Services reported 3,246 new positive cases, exceeding Thursday's single-day high of 2,519 cases.
• Florida health officials added 3,822 new cases Friday morning, surpassing its previous single-day high of 3,207 cases also reported on Thursday.
• More states are reporting record-setting daily numbers of Covid-19 cases as infections spread at an alarming rate.

Arizona, Florida, California and Nevada reported record spikes in confirmed Covid-19 cases on Friday as states continue their phased reopenings and ramp up testing.

The Arizona Department of Health Services reported 3,246 new positive cases, exceeding Thursday's single-day high of 2,519 cases. Florida health officials added 3,822 new cases Friday morning, surpassing the state's previous single-day high of 3,207 cases also reported on Thursday.

California officials reported 4,317 new cases Friday that were confirmed on Thursday, topping the previous record of 4,084 reported on Thursday. The Nevada Department of Health and Human Services reported 410 new cases Friday afternoon, breaking its previous single-day high of 379 from Monday.

More states are reporting record-setting daily numbers of Covid-19 cases as infections spread at a rapid pace. The Centers for Disease Control and Prevention expanded its list of states where Covid-19 deaths are expected to accelerate over the next four weeks compared with the past four weeks. The list now includes Alaska, Arizona, Arkansas, Hawaii, North Carolina, Oregon, South Carolina and Utah. 

While some state and federal leaders have attributed the rise in the number of confirmed coronavirus cases to increase in testing, many are seeing a climb in hospitalizations. This metric, like new cases and deaths, is also considered an important measure of an outbreak because it helps health officials gauge how severe it may be. 

Arizona

Arizona has quickly become one of the hardest-hit areas in the U.S. as new coronavirus cases continue to rise rapidly. Some hospitals in the state are nearing capacity, reporting a record number of patients in ICU beds on Thursday, which accounts for 84% of the state's capacity. 

Republican Arizona Gov. Doug Ducey announced new policies on Wednesday that allow local officials to require that residents wear masks and follow social distancing rules in public and in businesses.

Ducey also acknowledged that the virus is spreading more quickly than previously thought. 

"I said two weeks ago that there is not a trend here," Ducey said Wednesday evening while presenting a chart of daily new cases across the state. "Looking at the last two weeks of data, there is a trend. And the trend is headed in the wrong direction and the actions we're going to take are intended to change that direction and reverse this trend."

To help curb the spread of the virus, the governor announced plans to ramp up testing as well as contact tracing, a process whereby health officials contact infected people to try to identify the source of infection and others who might have been infected. 

However, some health officials are concerned that the virus has already reached a level of infection that will be hard to control.

Former Food and Drug Administration Commissioner Dr. Scott Gottlieb tweeted on Friday that Arizona has entered a "period of steep growth in its Covid epidemic."

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Gottlieb told CNBC on Thursday that the hardest-hit areas are now "on the cusp of losing control. Arizona, Houston, Austin, parts of Florida certainly look very concerning right now," he said.

Florida

Florida added nearly 4,000 new cases on Friday, bringing the state's total to 89,748 according to data from the Florida Department of Health. The state also reported 3,104 deaths and 12,774 hospitalized patients as of Friday. 

Florida was among the first states to reopen, allowing most restaurants and businesses to restart with limited capacity on May 4. The majority of the state is currently in "phase 2" of reopening.

Earlier this week, Republican Gov. Ron DeSantis said the state would not reimplement more restrictions or delay its reopening progress.

"We're not shutting down. We're going to go forward. ... We're not rolling back," the governor said at a news briefing Tuesday. "You have to have society function."

On Friday, DeSantis said that the median age of those who tested positive for Covid-19 has fallen from 65.5 years old in March to 37 in June. 

"That median age is plunging even further," he said at a news briefing and added that the average will continue to fall. "I think it's important for people to understand, a lot of the people who are testing positive now are not symptomatic."

DeSantis said the rise in infection among the state's younger population is due to "erosion of social distancing." 

"I'm definitely seeing when I'm out and about that people are not necessarily adhering to social distancing guidelines, that they're not necessarily wearing a mask or wearing it correctly," said Cindy Prins, an associate professor of epidemiology at the University of Florida. 

The governor attributed the increase in cases at least partly to increased testing. While the positivity rate has risen, he said the numbers are different among each demographic.

The state has tested or offered a test to every resident and staff at nursing homes, according to DeSantis. He said the key is to keep the infection rate low among the elderly and those at high health risks. 

During the briefing, the governor reassured residents that there's "plenty hospital capacity."

"We have twice as much capacity in the hospitals throughout the state of Florida today than before the pandemic began," he said. 

However, despite the increase in the number of tests being administered each day in Florida, the percent of people with positive test results has also increased. In fact, it has doubled since early June. 

"If you go back over the last two weeks, I don't think there's been a really significant increase in testing on a weekly basis if you add up those numbers, and yet it does seem that we've definitely had a jump in cases and people being identified," Prins said.

"I don't think you can say at least the week or so of cases is because of an increase in testing, I don't think that really holds out with the data."

California

After reporting more than 4,000 new cases for the first time on Thursday, California set a new record-high of 4,317 confirmed cases on one single day. The state announced a total of 165,416 positive Covid-19 cases and at least 5,360 total deaths.

California Gov. Gavin Newsom issued a statewide order on Thursday requiring people to wear a face covering in most indoor settings and outside when physical distancing is not feasible. He said too many residents have started to venture out in public without any masks. The order does not clarify how the state plans to enforce the rule or whether people will be fined for not complying. 

"Science shows that face coverings and masks work," Newsom said. "They are critical to keeping those who are around you safe, keeping businesses open and restarting our economy."

Nevada

Friday's number of new coronavirus cases marked the first time Nevada reported more than 400 cases on a single day. The state now has a total number of 12,486  confirmed infections and 478 deaths. 

Nevada Gov. Steve Sisolak asked his medical advisory team to "evaluate potential options for enhanced face covering policies" on Friday to mitigate the spread of the coronavirus. 

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As part of Nevada's reopening guidelines,  face coverings are required for employees when interacting with customers. However, they are "strongly encouraged" and not mandatory for the general public. 

— Graphics by CNBC's Nate Rattner