Covid-19 has "brought this nation to its knees," Dr. Robert Redfield, director of the US Centers for Disease Control and Prevention, said Tuesday.

The country is probably going to spend about $7 trillion "because of one little virus," Redfield said during a House Energy and Commerce Committee hearing.

"We've all done the best that we can do to tackle this virus."

Redfield's comments were made as half of US states are seeing spikes in new coronavirus cases -- and it's not just due to increased testing, health officials say.

As of Tuesday, 25 states have recorded higher rates of new cases compared to last week: Arizona, California, Colorado, Delaware, Florida, Georgia, Hawaii, Idaho, Kansas, Michigan, Mississippi, Missouri, Montana, Nevada, Ohio, Oklahoma, Oregon, South Carolina, Tennessee, Texas, Utah, Washington, West Virginia, Wisconsin and Wyoming.

And no state has effectively transitioned from stay-at-home orders "to a public health model of testing, tracking, isolating and quarantining," said Dr. Richard Besser, former acting director of the US CDC.

"We have to figure out how to make that transition in a successful way, or every state that reopens -- even those that have done a really good job at tamping this down -- are going to see pretty dramatic rises," Besser told CNN Tuesday.

"And we're going to end up back to where we were."

If the U.S. doesn't get control of the coronavirus pandemic by fall, "you're essentially chasing after a forest fire," Dr. Anthony Fauci told the House committee Tuesday.

The goal would be to get complete control of the virus instead of just mitigating it, which is happening now, said Fauci, who is director of the National Institute of Allergy and Infectious Diseases.

Redfield said the virus has highlighted decades of underinvesting in the "core capabilities of public health data." Now is the time to fix the broken system, he added.

"This needs to be a partnership. It's not all the burden of the federal government to invest in public health at the local level," Redfield said. In reality, "if your funding of CDC was to go away tomorrow, public health infrastructure across this nation would just crash."

"We're right now the backbone of it."

Nationwide, more than 2.3 million people have been infected with coronavirus, and almost 121,000 have died, according to data from Johns Hopkins University.

"The next couple of weeks are going to be critical in our ability to address those surgings that we're seeing in Florida, in Texas, in Arizona and in other states -- they're not the only ones having difficulty," Fauci said.

During Fauci's testimony in Tuesday's hearing, the nation's top infectious disease expert made a plea to all Americans:

"Plan A: Don't go in a crowd. Plan B: If you do, make sure you wear a mask."

Why the timing of these surges makes sense

Health experts say the spikes in new cases now coincide with states starting to reopen several weeks ago -- with many people refusing or abandoning safety measures such as wearing masks and social distancing.

And while health officials are reporting jumps in cases among younger people, Redfield said Tuesday more than half the nursing homes in the country -- over 7,000 -- have a Covid-19 patient in them.

"Two weeks ago, we had 17 states with increasing cases," said Michael Osterholm, director of the Center for Infectious Disease Research & Policy at the University of Minnesota.

Now, that number has jumped to at least 25 states. "And we're likely to move more states into that category of increasing cases very shortly," Osterholm said Tuesday. "So, we are seeing what in a sense is the reaction in the virus to opening up and having much more contact with each other."

After a new exposure to this virus, it can take up to two weeks for symptoms appear. After that, people might not get tested immediately. Then, it can take even longer for severe cases to require hospitalization.

Deaths from new Covid-19 exposures often don't get reported until several weeks after the new cases have been reported.

While health officials expected new cases as states reopened, many did not expect new cases and hospitalizations to rise so dramatically in some places.

Arizona set a new record this week for the number of people hospitalized on a given day with Covid-19 -- about 2,000, according to data from the COVID Tracking Project. The state's seven-day moving average of hospitalizations is also going up.

"People are being admitted to hospital beds and being admitted to ICU (intensive care unit) beds faster than they're being discharged," said Will Humble, executive director of the Arizona Public Health Association.

With about 84% of the state's ICU beds already full, Humble said he's worried hospitals will go into "crisis standards of care," which basically means "lower care for everybody, not just people with Covid-19."

California recorded more than 35% of its total infections from the entire pandemic in just the past two weeks. The state on Monday recorded 5,019 confirmed coronavirus cases, yet another daily high, according to data provided by California Department of Public Health. Hospitalizations are also at their highest level for Covid-19 patients.

It's not just increased testing

Some politicians have attributed spikes in new cases to increased testing. But in many places, the number of new Covid-19 cases are disproportionately higher than the number of new tests being performed, researchers say.

"In many states, the testing is increasing, but the percentage of those people who are positive is actually going much higher," Osterholm said.

"This is not an artifact of just more testing at all."

Even with the increased testing, the country is still "way behind the virus," a former US Health and Human Services secretary says.

"We are still reacting. We're not ahead of it," Kathleen Sebelius said.

"The only way to get ahead of the virus is to tamp way down the cases in any area, and then test like crazy when a case appears, contact trace, and make sure you quarantine. We can't do that yet because we are still finding all kinds of people who have the virus."

'Moving very fast in the wrong direction'

What's happening in Arizona and other states could erase much of the progress made during weeks of stay-at-home orders.

"The number of new cases had been stabilizing in early May, and actually the positivity rate (in testing) had been improving," Humble said.

"We came out of our stay-at-home order in the middle of May, and what we saw happening was that around May 26, that increase in cases that corresponded with the end of the stay-at-home order."

Florida, a popular destination for beachgoers, is also grappling with a surge in new cases and hospitalizations. The Sunshine State now has "all the markings of the next large epicenter of coronavirus transmission," researchers say.

And in Texas, where the rates of daily new cases and new hospitalizations are rising, Houston is "moving very fast in the wrong direction," Mayor Sylvester Turner told CNN affiliate KTRK.

After Houston reported its highest daily count of new Covid-19 cases, Turner called on residents to take safety measures more seriously.

"This is a health care crisis," he said. "Quite frankly, your failure, for example, to wear masks ... or to engage in social distancing directly impacts on somebody else."

Where states are seeing steady or improving numbers

In 12 states, the numbers of new daily cases have generally held steady in recent days: Alaska, Arkansas, Illinois, Iowa, Kentucky, Minnesota, Nebraska, New Mexico, North Carolina, North Dakota, Pennsylvania and Virginia.

And in 13 states, the numbers of new cases are generally declining: Alabama, Connecticut, Indiana, Louisiana, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Rhode Island, South Dakota and Vermont.

"New York went from one of the highest infection rates in the country to one of the lowest because we made decisions based on science, not politics," Gov. Andrew Cuomo said Tuesday.

"We're seeing in other states what happens when you just reopen with no regard for metrics or data -- it's bad for public health and for the economy, and states that reopened in a rush are now seeing a boomerang."

Cuomo is consider forcing visitors from high-transmission states to quarantine upon arrival to New York state, he said. (CNN)

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