At least four states combined data from two different test results, potentially providing a misleading picture of when and where coronavirus spread as the nation eases restrictions.
More than 1.5 million people in the United States have tested positive for coronavirus and over 93,000 have died, according to Johns Hopkins University.
Virginia, Texas, Georgia, and Vermont have said they've been adding two numbers to their totals: viral test results and antibody test results.
Viral tests are taken by nose swab or saliva sample, and look for direct evidence someone currently has Covid-19. By contrast, antibody tests use blood samples to look for biological signals that a person has been exposed to the virus in the past.
Combining the two tests' results into one total could provide an inaccurate picture of where and when the virus spread. It could also overstate a state's ability to test and track active infections -- a key consideration as states ease coronavirus restrictions. Experts have consistently emphasized that for states to reopen safely, adequate testing and tracing is needed.
"You only know how many cases you have if you do a lot of testing," said Elizabeth Cohen, CNN's senior medical correspondent. "If you put the two tests together, you fool yourself into thinking you've done more testing than you have."
Georgia Gov. Brian Kemp addressed the data reporting concerns Thursday, saying "Georgia families, businesses, local leaders, and the press deserve accurate data" and health officials are working to produce that information.
"They are taking massive amounts of data from countless sources, putting it into an accessible format under a global spotlight -- all at breakneck speed," Kemp said.
Texas, Virginia and Vermont have said they've recognized the data issue and moved to fix it in the past few days. In Georgia, health officials said they've been adding antibody tests to their "total tests" number in line with methodology from the Centers for Disease Control and Prevention.
The CDC has not responded to CNN's request for comment on whether its guidance includes adding antibody tests to total test numbers. On the CDC website, the database provides daily test results without a breakdown of whether they're viral or antibody.
Lockdown delays cost about 36,000 lives, study says
A Columbia University model suggests that if the United States had started social distancing just a week earlier, it could have prevented the loss of at least 36,000 lives to the coronavirus.
"Our findings underscore the importance of early intervention and aggressive response in controlling the Covid-19 pandemic," the researchers wrote in the report.
The model depicts the transmission of the virus throughout the US using epidemiological modeling to gauge transmission rates from March 15 to May 3, lead researcher and epidemiologist Jeffery Shaman told CNN's Don Lemon.
Some governors said knowing what the model suggests would have changed their thinking on when to start social distancing measures.
"If I would have known then what I know now, I would have shut down sooner," Rhode Island Gov. Gina Raimondo told reporters.
"There's no doubt about that," she added. "But I didn't."
New York Gov. Andrew Cuomo suggested if everyone knew more, a lockdown should have started on December 31. "If this country knew more and knew it earlier, I think we could have saved many, many more lives," Cuomo said Thursday.
Mayor considering a shelter-in-place order
The mayor of Alabama's capital said Thursday he's considering issuing a local shelter-in-place order after health officials saw an increase of new cases in the past two weeks.
"My hope is that we don't have to do that," Montgomery Mayor Steven Reed told CNN on Thursday.
The city has a shortage of open beds in intensive care units, Reed said, due to the number of Covid-19 patients.
In a news conference Wednesday, Reed said the city's health care system is "maxed" and if you need an ICU bed, "you are in trouble."
The mayor said he believes the spike of cases is related to the state loosening restrictions -- a move he described as premature.
"I would have liked to see a more cautious approach to us reopening our economy," he told CNN's Brianna Keilar.
As of Thursday afternoon, Alabama was one of 17 states that had registered an upward trend in average daily cases -- a rise of at least 10% -- over the previous seven days, according to an analysis of Johns Hopkins University data.
"We're still in a tough battle and now is not the time for us to relax," Reed said.
Twelve states' average daily cases dropped more than 10%, while the rest were level or near level, the data showed.
States reopening public places at their own pace
States are easing more restrictions ahead of Memorial Day weekend.
All 50 states have now taken some steps to reverse the restrictions they placed on businesses and services, with Connecticut joining the list on Wednesday.
On Friday, North Carolina will allow restaurants to open their dining rooms with distancing rules. Barber shops and salons also may open with limitations.
Alaska is allowing all businesses to reopen, as well as houses of worship, libraries, museums and sporting activities, starting at 8 a.m.. Alaska has the fewest cases of all states and has reported single-digit new cases since mid-April.
Alaskans are encouraged to take precautions, such as distancing and wearing masks in public places. Visitation to prisons and senior centers will be limited.
Iowa Gov. Kim Reynolds intends to allow movie theaters, zoos, aquariums, museums and wedding venues to reopen Friday. Swimming pools will be allowed to open for laps and lessons as well. Bars can reopen May 28, and school-sponsored activities, such as sports, can resume June 1, she said.
Indiana also plans to move ahead with opening a large swath of its economy Friday, but with restrictions such as limiting social gatherings to 100 people and dining rooms to 50% capacity, and omitting contact games from a list of sports allowed to resume.
But many cities remain under stay-at-home orders. In Baltimore, gatherings of more than 10 people are still prohibited and retail stores remain closed.