The United States topped 1 million confirmed cases of coronavirus Tuesday – nearly a third of the world's cases – as health authorities here and around the globe try to understand the full scope of who is at risk and who has been infected.

Reaching seven figures – 1,002,498 to be exact – is the latest milestone for the U.S., which has topped 57,000 deaths during the pandemic, according to the Johns Hopkins University dashboard. That's a number approaching the 58,220 Americans killed in the Vietnam War from 1955 to 1975.

And despite warnings from national health leaders that the country could face a second wave of the virus in late 2020, states and cities are drafting or implementing plans to get people out of their homes and back into mainstream life.

It's all happened in about three months. The country's first case was confirmed Jan. 21, and much of what we know about the virus is still subject to study and debate.

There are now six new symptoms the Centers for Disease Control and Prevention caution could be signs of the coronavirus: chills, repeated shaking with chills, muscle pain, headache, sore throat and a loss of taste or smell.

Shortness of breath was tweaked to "shortness of breath or difficulty breathing" by the CDC, which recommends seeking "medical attention immediately" for trouble breathing, persistent pain or pressure on chest, bluish lips or face, or a new confusion or inability to awaken.

The daily spike in new cases had slowed in recent weeks, but April 24 saw a daily high for the U.S. with 36,200 cases reported.

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Testing pitfalls

According to Johns Hopkins University data, 5.6 million of the estimated 328 million people in the country have been tested for the virus. Still, testing is not as widely available as President Donald Trump says and many governors say they're running low on testing equipment.

The lack of testing "is probably the Number 1 problem in America, and has been from the beginning of this crisis," said Maryland's Republican Gov. Larry Hogan, the chairman of the National Governors Association.

The number of cases would be substantially higher if testing was more readily available and steady increases are to be expected as testing expands further.

Will we ever have an accurate number of cases?

Dr. Tom Ingelsby, director of the Center for Health Security of the Johns Hopkins Bloomberg School of Public Health, said numbers represented on the Hopkins dashboard don’t accurately portray the total amount of cases and deaths in the U.S.

“We know at this point that there has been a very, very important undercounting of total cases,” he said.

He said the lack of testing mild and moderate cases is the main driver of this misrepresentation, as hospitals only tests patients who are in need of critical care. Ingelsby also doesn’t doubt that there’s an undercounting of deaths as well, although probably less so.

The first phase of testing has been about determining who has COVID-19. The next will be about who had it. Instead of looking for the virus itself, the second phase will look for signs in our blood that we developed antibodies to fight the virus.

However, antibodies for the coronavirus that causes COVID-19 look very similar to other coronavirus antibodies that cause illnesses such as the common cold.

Tests could mistakenly identify antibodies as being for the coronavirus that causes COVID-19, producing a false positive, said Dr. Raed Dweik, chairman of the Respiratory Institute at the Cleveland Clinic. As antibody testing develops further, the accuracy should improve.

The implementation of widespread antibody testing will face similar challenges as testing for the virus, and Dweik said it will take more time to develop a test that can accurately detect the right antibodies.

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Meanwhile, states big and small are evaluating when they can restart their economies after weeks in lockdown necessitated by the coronavirus.

In Texas, Gov. Greg Abbott said Monday he will let his stay-at-home order expire Thursday as the state begins a phased reopening that will permit malls, restaurants and movie theaters to operate starting Friday, with occupancy limitations.

In Ohio, Gov. Mike DeWine announced a partial reopening beginning Friday, with some openings delayed until May 12. Dental offices and veterinarian clinics are allowed to open Friday. General offices, distribution centers, manufacturers and construction companies can open May 4. Retail stores, consumer and service businesses will have to wait until May 12.

Masks will be required for workers and shoppers.

“No masks, no work, no service, no exception,” DeWine said.

However, New Jersey is not ready to take those steps, Gov. Phil Murphy said Monday. The state ranks second to New York for the most coronavirus cases and deaths in the country, and Murphy suggested a phased reopening may not take place until Memorial Day weekend. He did not commit to a timeline.

Contributing: Jorge Ortiz, Ryan Miller, Joel Shannon, USA TODAY