Coronavirus cases grow in more than 30 states as the U.S. sets a record for average daily cases

Coronavirus cases are growing in more than 30 states, based on a seven-day moving average, as governors in Florida and Arizona place a hold on their reopenings and Texas tightens restrictions once again.

As of Thursday, the nation's seven-day average of new Covid-19 cases increased more than 38% compared with a week ago, according to a CNBC analysis of Johns Hopkins University data, reaching a record high average of more than 33,000 daily new cases.

Cases were growing by 5% or more, based on the change in average new cases compared with last week, in 35 states across the country, including California, Florida, Georgia, Texas and Nevada. Those states were also among the 13 that hit record highs in their average number of daily new cases on Thursday. 

Another factor that is watched carefully is hospitalizations, which can indicate how severe cases are in an area. This data can lag the number of new cases. 

Hospitalizations from Covid-19 were growing in 15 states as of Thursday, according to a CNBC analysis of data compiled by the Covid Tracking Project. 

While the rise in daily case numbers could reflect increased testing in certain locations, some states are reporting higher positivity rates. The positivity rate indicates the percentage of tests that come back positive in a specific region. Epidemiologists say this number can indicate how broadly the virus is spreading throughout a community. 

On Friday, members of the White House coronavirus task force warned young people in states with rising case numbers that while they may not be at risk of serious illness, they could infect someone who is. 

"People are infecting other people and ultimately you will infect someone who's vulnerable," Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said during a press briefing. 

Vice President Mike Pence said that there are 16 states reporting a rise in the total number of cases and the percent of tests coming back positive. He said that roughly half of the new cases are Americans under the age of 35, which is "at a certain level very encouraging news" because experts say that younger people are less susceptible to serious illness from the virus. 

California's positivity rate has slightly increased to 5.1% over the last two weeks as the state reports record increases in daily new cases. Texas' positivity rate exceeded 10% on Wednesday, which is a level that raises a "warning flag," according to Gov. Greg Abbott. Arizona's rate is also averaging above 10%, according to the state's department of health.

On Friday, Abbott announced Texas would roll back some of its reopening, only a day after he said he would place the state's reopening plan on pause.

"As I said from the start, if the positivity rate rose above 10%, the State of Texas would take further action to mitigate the spread of COVID-19," Abbott said in a press release. "At this time, it is clear that the rise in cases is largely driven by certain types of activities, including Texans congregating in bars."

All bars and similar establishments that receive more than 51% of their gross receipts from the sale of alcoholic beverages are required to close by 12 p.m. Friday, according to the order. Rafting and tubing businesses must close and outdoor gatherings of 100 or more people must be approved by local governments, with certain exceptions.

Abbott announced on Thursday that the state would pause any further reopening measures, and he ordered all licensed hospitals in four counties that include the state's largest cities — Houston, San Antonio, Dallas and Austin — to postpone elective procedures in order to preserve hospital capacity for Covid-19 patients.

Texas reported an 79% increase in its weekly average of coronavirus cases on Thursday, averaging 4,757 daily new cases, according to Hopkins data. 

When asked about Florida's reopening, Gov. Ron DeSantis said that the state doesn't have plans for continuing its step-by-step reopening plan. He added that the state "never anticipated" continuing to move forward at this point.

"We are where we are. I didn't say we were going to go on to the next phase," DeSantis said at a news briefing. 

Florida is averaging about 4,013 daily new cases as of Thursday, which is about a 67% increase since one week ago, according to Hopkins data. DeSantis has allowed retailers, restaurants, gyms and personal care services to reopen at reduced capacity.

Arizona Gov. Doug Ducey said on Thursday that the state's hospitals are seeing additional stress and are "likely to hit surge capacity very soon." 

"Covid-19 is widespread in Arizona. It's in all 15 of our counties. It's growing, and it's growing fast across all age groups and demographics. Anyone can get this virus, and anyone can spread this virus," Ducey said at a press conference. 

If the state's reopening were a traffic light, Ducey said that it would be in the "yellow" or "yield" position. 

"To proceed with caution, to go slower, to look both ways," he said. "This virus is everywhere — it is likely in this room right now — and the actions that you take as a citizen will make a difference."

— CNBC's Nate Rattner contributed to this report.