New studies on the spread of the coronavirus in U.S. hot spots suggest that many more people in the New Orleans area may have been infected by the virus in recent weeks than shown in the official count of known cases.

The findings of recent studies in New York, Los Angeles, Miami and Santa Clara, California, while preliminary, show that far higher percentages of those cities' residents have antibodies for the disease, indicating that many mild or asymptomatic cases went undetected by public health officials.

LCMC Health, the City of New Orleans Health Department and Louisiana State University Health Sciences Center (LSUHSC) begin testing during the first day of free walk-up community COVID-19 testing at the parking lot of Xavier University's Convocation Center in New Orleans, Tuesday, April 21, 2020. The mobile coronavirus testing will continue through Friday before they move to the next neighborhood. They plan to visit at least six different underserved neighborhoods. STAFF PHOTO BY SOPHIA GERMER ▲

And while infectious-disease experts are skeptical of some of the studies' results, many nevertheless say that the broad conclusions in those hot spots likely apply to New Orleans, the epicenter of Louisiana's coronavirus outbreak.

As of Saturday, the Louisiana Department of Health has reported 6,297 known cases of coronavirus in Orleans Parish, meaning that roughly 1.6% of the city's population has tested positive for the virus. Ballpark estimates based on the studies conducted in those other cities suggest that the true number of the city's population that has been infected with COVID-19 could range anywhere from around 10,000 to as high as 80,000 residents.

“New Orleans, I have a feeling, is somewhere in between,” said Tulane University epidemiologist Susan Hassig. “I think the variability in those examples is indicative of how the epidemic of coronavirus might play out in different environments.”

Hassig and other experts are quick to caution that differences in New Orleans' population density, testing rates and other factors make arriving at a true estimate difficult without a study focused squarely on the New Orleans area. Some others are concerned about the veracity of the antibody tests.

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Still, the findings offer a note of hope amid the ever-rising death toll, because they appear to show that the disease, while highly contagious, is a bit less deadly.

If many more people have already had it, Gov. John Bel Edwards and other public officials may be more comfortable in reducing restrictions and reopening parts of the economy — though that will also depend on the extent to which having COVID-19 provides protection from getting it again.

The new estimates of the scope of infections are based on studies released in recent days. A state survey in New York City showed about one in five New Yorkers has antibodies for COVID-19. In Santa Clara, Calif., a recent study conducted at Stanford University suggested somewhere between 2.5% and 4% of the population might have been infected. Another study in Los Angeles by the University of Southern California found that between 2.8% to 5.6% of the adult population might carry the antibodies.

About 6% of Miami's population may have had the virus, researchers at the University of Miami said Friday.

Dr. Jeffrey Shaman, a Columbia University epidemiologist and a leading modeler of the coronavirus’s spread, is among many scientists who are dubious of some of the conclusions of the Santa Clara study, which found that the actual infection rate in Santa Clara County was between 50 and 85 times higher than the known rate.

Shaman believes the “specificity” of the test used was not as good as the manufacturer claimed.

“I think the numbers could be off considerably,” he said.

That said, Shaman said there is a growing consensus that the real share of infected people in the U.S. is much higher than the share known to be infected.

In places in the country where testing has been relatively robust, like in New York and New Orleans, the share of the populace known to be infected is as high as 2% to 3%. Shaman believes the true numbers in New York City could be 10 times higher than the known rate, or around 20%, in keeping with the findings of the New York study.

“Those numbers are all consistent with what my group and others have been talking about,” he said.

In New Orleans, the numbers will likely add to the guessing games already underway among socially distanced residents about whether coughs and colds in recent months were really something more sinister.

It’s not unusual to have a cough in New Orleans in early spring. The air is filled with respiratory-ravaging pollen. The flu, so prevalent that the Centers for Disease Control and Prevention sent a team of experts to the city this year, is at its height. And common colds circulate among a city still recovering from Carnival.

Boards cover windows of businesses around the French Market area of the French Quarter amid the coronavirus pandemic in New Orleans, Sunday, March 29, 2020. STAFF PHOTO BY SOPHIA GERMER ▲

But in light of the coronavirus pandemic that peaked here in March, many are asking, "Was it the post-Mardi Gras crud, or was it the coronavirus?"

Hassig is giving second thoughts to respiratory symptoms in early spring she initially chalked up to allergies.

"I had a hacking cough when pollen was exploding off the oak trees," she said. "Was that COVID? I don't know."

People wait in line during the first day of free walk-up community COVID-19 testing at the parking lot of Xavier University's Convocation Center in New Orleans, Tuesday, April 21, 2020. The mobile coronavirus testing by LCMC Health, the City of New OrleansÕ Health Department and Louisiana State University Health Sciences Center (LSUHSC) will continue through Friday before they move to the next neighborhood. They plan to visit at least 6 different underserved neighborhoods. STAFF PHOTO BY SOPHIA GERMER ▲

Determining exactly how many people in the city have been exposed to coronavirus is important in gauging who might be protected from the disease and when the population will reach herd immunity status, a signal it’s safe to return to a more normal way of life.

And while a high infection rate would, at this point, be good news for the city, experts warned that even 20% would be far off from the estimated 60% to 80% needed to achieve herd immunity — in which the virus hits a dead end because infected people are not mingling with enough noninfected people — for a disease as contagious as coronavirus.

On Saturday, the World Health Organization also cautioned that there wasn't yet evidence that catching COVID-19 will necessarily prevent someone from catching it a second time.

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The retroactive search for infections relies on antibody tests, only four of which are approved by the Food and Drug Administration. And experts warn that we’re still in the Wild West of developing the tests and figuring out what kind of immunity, if any, antibodies confer.

“The call for this type of testing is completely understandable,” said Dr. Joe Kanter, an assistant state officer the Louisiana Department of Health. “How nice would it be in this outbreak to take a test and know how many of us are immune? The challenge is that we’re just not there yet.”

One thing is clear: Antibody tests only offer a fragmented view of a disease Hassig says is like a complicated jigsaw puzzle.

“We have the edges in place and have a few pieces in the interior,” said Hassig. “But we’re not entirely sure what the picture is.”

Residents in Louisiana can expect cases to go up like clockwork as soon as businesses start to reopen, she said. But maintaining practices like wearing a mask in public and stringent hand-washing will help keep infections down.

“No matter what they do, cases are going to go up,” said Hassig. “The virus is still here."