Yanti Turang, an emergency room nurse at a New Orleans hospital, walked out into the parking lot in full protective gear early this month to meet a woman with flulike symptoms who had just returned home after a layover in South Korea. The woman was immediately taken to an isolation room.

Around the same time, a man who had never left the country and had been in New Orleans throughout the just-concluded Mardi Gras season, showed up at the ER with a high fever and a dry cough. He was placed in a neighboring room and cared for by hospital workers without any special gear.

To everyone’s relief, the woman who had traveled through Asia tested positive for the standard flu. The man, however, did not, Turang said. His symptoms improving but his diagnosis unclear, he was told to take Tylenol and get some rest. And he was sent back out into the city.

Turang does not know what became of that man, but he was on her mind two days later when the first confirmed case of the novel coronavirus was announced in Louisiana — another person, at another hospital. Coronavirus had been in the city all along. Since then, the outbreak here has become one of the most explosive in the country.

According to one study, Louisiana, with more than 2,300 cases as of Thursday afternoon, is experiencing the fastest growth in new cases in the world. Gov. John Bel Edwards said Tuesday that the current trajectory of case growth in Louisiana was similar to those in Spain and Italy. This week, President Donald Trump approved the governor’s request for a major disaster declaration, which unlocks additional federal funding to combat the outbreak.

The situation in and around New Orleans is particularly acute, with the city reporting 997 confirmed cases as of Thursday afternoon, more than the total number of cases in all but 13 states. Hospitals are overwhelmed and critical safety gear is running low.

Orleans Parish, which shares its borders with the city of New Orleans, has suffered the highest number of deaths per capita of any county in the nation. Of the parish’s 46 deaths — more than two times the death toll of Los Angeles County — 11 are from a single retirement home, where dozens more residents are infected. In a grim irony, there is a rising suspicion among medical experts that the crisis may have been accelerated by Mardi Gras, the weekslong citywide celebration that unfolds in crowded living rooms, ballrooms and city streets, which this year culminated Feb. 25.

It is the city’s trademark expression of joy — and an epidemiologist’s nightmare.

“I think it all boils down to Mardi Gras,” said Dr. F. Brobson Lutz Jr., a former health director of New Orleans and a specialist in infectious disease. “The greatest free party in the world was a perfect incubator at the perfect time.”

As a kind of ghostliness settles over a locked-down nation, the effect of social distancing feels particularly jarring in New Orleans, a city that runs on intimacy — from the deep webs of kinship and geography that connect families and neighborhoods to the fleeting threads that bind strangers and regulars in storied restaurants and packed, sweaty clubs.

Now the grand restaurants are offering takeout, if they are open at all. The clubs are silent. Bourbon Street is just another lonely street, its only crowds the hordes of rats that have become increasingly brazen in their hunt for food.

‘Everybody talks to everybody’

Dr. Susan Hassig, an epidemiologist and associate professor at the Tulane University School of Public Health and Tropical Medicine, said there were other likely reasons, beyond Mardi Gras, that may explain why New Orleans has been so hard-hit — the dense, compact nature of the city; its tourism industry; its port, which connects it to the world; and the way people connect culturally.

“Everybody talks to everybody, which means you stop and you have a conversation and then you move on and have a conversation with somebody else,” said Hassig, who rode in a Mardi Gras parade with the Krewe of Muses this year.

Turang, the emergency room nurse, who worked in Sierra Leone during the Ebola epidemic in 2015, said doctors and nurses now talk of the patients who had shown up to hospitals between Mardi Gras and the announcement of that first case on March 9, people with moderate flulike symptoms who had tested negative for the flu.

“We were blindsided,” she said.

That first confirmed case in Louisiana was announced less than two weeks after Fat Tuesday. Around the same time, reports had begun popping up around the South — Tennessee, Arkansas, Texas — of people who had tested positive after recently returning from New Orleans.

‘Something wasn’t right’

The first people to test positive in New Orleans, according to Dr. Jennifer Avegno, the city’s health director, had not recently returned from anywhere. But their array of unusual symptoms had troubled doctors.

“They just had a sense that something wasn’t right,” Avegno said. “It became clear pretty quickly that there was community spread.”

Within days, the state’s schools were shut down and large public gatherings in New Orleans were banned.

As testing ramped up, the number of cases in Louisiana surged. A medical worker at the city jail tested positive, as did a founder of the Grammy-winning Rebirth Brass Band. Sean Payton, the coach of the New Orleans Saints, announced that he had tested positive. The archbishop of New Orleans did, too.

The growth rate of new infections in Louisiana was the fastest in the world when comparing areas during the two weeks that followed their first confirmed diagnosis, according to a recent study by Gary Wagner, an economics professor at the University of Louisiana at Lafayette. In a small and close city like New Orleans, that means that nearly everyone knows someone who has been infected.

The attendant tragedy of the pandemic — economic devastation — has been following close behind.

“Our food banks say they’ll be out of food by next week,” said Mayor LaToya Cantrell of New Orleans, adding that the city was estimating a budget deficit of at least $100 million next year, given the vanishing sales tax revenues.

“And,” the mayor continued, “we have hurricane season coming in June.”