Healthcare workers from the University of South Florida conduct COVID-19 testing in Tampa, Florida, on Thursday.
Redfield said there are increasing concerns as the USA witnesses a spike in cases.
"CDC also clarified the list of other conditions that might increase a person's risk of severe illness, including additions such as asthma, high blood pressure, neurologic conditions such as dementia, cerebrovascular disease such as stroke, and pregnancy", it said.
In total, the U.S. has confirmed more than 2.4 million cases of Covid-19, the diseased caused by the novel coronavirus, according to the university.
California governor declares budget emergency due to COVID-19 pandemic
As of Thursday, California experienced a 32% increase in total COVID-19 hospitalizations over the past 14 days. But deaths are usually a lagging indicator in outbreaks, only spiking after infections and hospitalizations.
"Understanding who is most at risk for severe illness helps people make the best decisions for themselves, their families, and their communities", said CDC Director Robert Redfield in a statement.
It came as the USA reported a record daily number of cases, and Texas paused the reopening of its economy due to a "massive outbreak". The national number of daily coronavirus case reports reached a new high Friday as well at nearly 40,000, according to data from Johns Hopkins University, and 33 states are now seeing the number of new cases grow from the week before.
Case counts continued to surge to record levels in many states, including Texas, Alabama, Missouri and Nevada.
Abbott also suspended elective surgeries at hospitals in some parts of the state to free up bed spaces. The counties are home to major cities: Houston, Dallas, San Antonio and the state capital, Austin. President Trump even stated this week the virus was "fading away", despite clear evidence the number of cases is on the rise.
Florida governor points to higher case numbers in 'younger folks'
The new data from the state also continues to show how disproportionately vulnerable the elderly are to the virus. Bars in the Palm Beach, Broward and Miami-Dade counties haven't been allowed to reopen since mid-March.
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"This temporary pause will help our state corral the spread until we can safely enter the next phase of opening our state for business", he said.
"In the past, I don't think we diagnosed these infections", he said. "We are where we are". Orange County, home to Orlando, is averaging 353 new cases a day, compared with 73 two weeks ago. "So, it's possible that we're seeing a smaller proportion of infections in older people because there actually is less exposure".
While some of the increase is down to increased testing, the rate of positive tests in some areas is also increasing.
14 more Clemson football players test positive for coronavirus
Clemson said it had conducted a total of 430 coronavirus tests on athletes and staff members since the beginning of the month. There were 19 new confirmed cases since the last school update last week, with 14 of them coming from the football team.
Los Angeles County now has the highest number of cases in the country with more than 89,500 cases, according to public health data. Mr Newsom has made wearing a face mask mandatory in public.