With testing for coronavirus infections ramping up across the Louisiana, political leaders and hospital officials are starting to look ahead to a new type of test that will let patients know if they've developed immunity to the deadly virus.

Unlike the tests now on the market used to confirm if someone with symptoms does in fact have COVID-19, the blood test, officially a serology test, is used to establish whether someone has developed antibodies to the disease after infection.

Gauging that immunity is "critically important" when making decisions about loosening stay-at-home orders and other restrictions, Gov. John Bel Edwards said last week.

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Health experts have cautioned that restrictions won't soon be lifted even though recent days have offered hope the state has started to "flatten the curve" and slow the spread of the disease.

Deaths linked to coronavirus statewide rose 34 on Sunday to 840, the smallest increase since April 1, though weekend figures tend to be lighter and experts have warned not to read too much in single-day fluctuations. The number of patients with COVID-19 in hospitals — 2,084 people — rose by 17 patients.

Before pulling any triggers to reopen businesses or allow gatherings, Edwards said the state will need the new blood tests, as well as far more of the coronavirus tests now in use and extensive tracing of the disease's spread.

“We’re going to be looking to avail ourselves of that testing as broadly as we can once it becomes available,” Edwards said.

State health officials are already working with labs to gain serology test capability, according to Assistant Public Health Secretary Alex Billioux.

Ochsner Health System executives said last week they have ordered serology tests and expect them to arrive within two weeks. Representatives from Tulane Medical Center and LCMC Health have said they were also interested in the new tests.

The U.S. Centers for Disease Control and Prevention began a pilot program in March to roll out serology testing on random samples of people in cities deemed COVID-19 hot spots. On Friday, CDC spokesman Scott Pauley said the first stage of that program is focusing on Washington state and New York City. The feds have said a second stage is coming in the summer.

"The second stage will expand to include serologic testing in more areas with high numbers of people with diagnosed infections," Pauley said.

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Last week, Mayor LaToya Cantrell criticized the federal government for overlooking New Orleans, a hot spot for the virus, when it comes to recovering financially from the coronavirus. She said the city needs all the testing it can get.

"We are ripe to receive and be a pilot as it relates to antibody testing in our parish and in the state," Cantrell said.

The test, if used widely, will give officials the clearest picture yet of the disease’s grim march across Louisiana.

Thus far, the state has only tracked coronavirus cases by the number of people who are sick enough to be tested and by those who have died. Tests are typically only given to those with fever and severe shortness of breath, but studies have suggested that many people might be infected by the coronavirus and never show symptoms.

To understand the scope of infection, Louisiana and other states across the U.S. will need to test a representative sample of the thousands of people who may have had the disease but who were not sick enough for an initial traditional test or were sick before widespread testing was available.

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If used in the state, the new tests likely would still show the majority of residents have not been exposed to COVID-19. If that is the case, it means most people will still be at risk of catching the disease when restrictions are lifted, and the state will need to plan accordingly, Edwards said.

Even limited immunity tests can help hospitals better combat the coronavirus, particularly as major pharmaceutical companies have said they are at best several months away from a vaccine. For example, if frontline health care workers know they are immune, it could ease their anxieties as they treat patients, said Dr. Susan Hassig, a Tulane University epidemiologist who specializes in infectious diseases.

As more serology tests come online, Ochsner Health hospitals could begin collecting samples from former patients who had respiratory trouble and recovered but who could not be tested for COVID-19 because those tests weren't yet available in the state, said Ochsner Chief Medical Officer Robert Hart.

The tests can also help doctors identify immune people who can donate plasma to dangerously sick COVID-19 patients, a treatment the federal Food and Drug Administration has said may help, Edwards said. It's not clear how many Louisiana hospitals are doing the plasma transfusions, only recently given the nod by the FDA.

But within at least one Louisiana medical facility, the serology testing is underway, albeit on a very small scale.

LSU Health Sciences Center’s Cancer Center, in partnership with the National Cancer Institute, is collecting samples from up to 50 coronavirus patients for antibody testing, said Dr. Augusto Ochoa, the center's director.

The Cancer Institute hopes to collect 200 samples in all from coronavirus hot spots across the country to better understand immunity, Ochoa said.

"Right now, we are working with patients who know they have it and have tested positive for it,” though that could change, Ochoa said.

One of the biggest questions remains just how strong or long-lasting people's immunity will be.

In patients infected with the human coronavirus most similar to the new strain, SARS CoV-1, “the antibodies peak at around four months, and … decline slowly after three years,” said Dr. Preeti Malani, a member of the Infectious Diseases Society of America and a University of Michigan infectious disease physician.

That fact and studies of the new strain that causes the COVID-19 disease suggest that people won't get reinfected quickly. Still, "we don't fully know," Malani said.

The FDA has been inundated with requests from companies seeking permission to begin selling the new tests, and warned consumers last week that only one firm, Cellex, has received that clearance. Cellex has said it will begin shipping its 20-minute tests within weeks.

State and local officials said it was critical to vet tests before promoting their spread.

"These will be part of our recovery, but we also want to make sure they are reliable, and we can rapidly deploy them to those who need them first," said New Orleans Health Department Director Jennifer Avegno.

Potential pitfalls aside, U.S. Sen. Bill Cassidy, R-La., said the blood tests remains one of the best possible indicators of whether Louisiana can brighten its presently grim jobs outlook and restart life as residents know it.

“It’s part of the way we begin to reopen our economy,” Cassidy said at a recent online town hall hosted by The Times-Picayune | The New Orleans Advocate.

Staff writers Jeff Adelson and Bryn Stole contributed to this report.