Stanley Schwaner’s hard work and energy had brought his family’s failing New London grocery back from the brink, and the 29-year-old had a bright future.

On Sept. 21, 1918, he was at work early, getting ready for a busy Saturday. A slight cold annoyed him, and during the day his symptoms worsened. By 10 p.m. he was clearly ill, but when a co-worker urged him to go home, he refused, having business to tend to first.

Schwaner finally went to bed, and his condition deteriorated the next day. On Tuesday he was seen by a doctor, showed signs of improvement, then suffered a relapse.

By Friday morning he was dead.

“To hundreds of personal friends in New London and to his large staff of employees, the death of Mr. Schwaner came as a severe mental shock,” the New London Telegraph reported.

Over a dark stretch of weeks, the shock of sudden loss would recur many times in the region as, one by one, people fell ill and died. A century ago this month, Spanish influenza, the greatest plague in human history, reached southeastern Connecticut.

As people around the globe absorbed the battlefield horrors of World War I, then in its fourth year, an even deadlier event stole up on them. Descending in four waves, the 1918 flu pandemic sickened 500 million people worldwide, killing 50 million to 100 million, or 3 to 5 percent of the world’s population.

The first wave passed almost unnoticed, but the second was the deadliest, breaking out simultaneously in Europe, Africa and North America. Ground zero in Connecticut was New London, where the disease first appeared in the Navy population.

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The Naval Hospital on Garfield Avenue wasn’t new, but it was the product of recent events. Two years earlier, the submarine base had been established in Groton, and shortly afterward, the U.S. entered the war.

Faced with a sudden need to care for sailors flooding the region, the Navy approached an existing institution, Memorial Hospital, and leased it lock, stock and barrel. In April 1918, military doctors and nurses replaced the civilian staff and, just like that, the Navy had a hospital with 200 beds. Sooner than anyone knew, that wouldn’t be nearly enough.

Around Sept. 1, the hospital found itself managing a handful of influenza cases from the Experimental Station at Fort Trumbull, followed by a few more from the base in Groton. By Sept. 12, about 100 patients were being treated, and the base went under quarantine.

“It is thought to be a form of the so-called Spanish influenza which has developed at certain other ports and it has, evidently, been imported,” The Day noted.

The Navy’s wartime presence included a base at State Pier, where 300 men arrived Sept. 10 from the Boston Navy Yard, where the flu was raging. With nearly 7,000 men boarded in civilian homes, the disease spread quickly to the general population.

At first it didn’t seem worse than a routine epidemic. Cheery public-service ads advised not sneezing in people’s faces and urged the use of Vick’s Vaporub and Bromo Quinine tablets, whose curative powers were debatable at best.

The newspapers tried to laugh off the tremors of unease that were starting to spread.

“That a sad visitation has struck the region is undeniable,” The Day editorialized. “What do you expect in war times? Nothing but feathers and clover and plenty of succotash? Be thankful we haven’t bombs dropped on us.”

But hopes that the worst would pass in a few days soon faded. As flu brought pneumonia and pneumonia brought death, officials tried to downplay the increasingly frightening numbers.

“At present,” Navy Capt. T.W. Richards said, not so reassuringly, on Sept. 24, “there are 470 cases of influenza in the Naval hospital and the four annexes here. This figure shows a marked decrease ... as at the peak of the epidemic, figures ran as high as 596.”

The peak, however, had not yet arrived.

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From New London, the outbreak spread, first north then west, until in a few days the entire state was under siege. Soldiers traveling from Camp Devens in Massachusetts also infected scattered towns.

Some rural places were spared, while others were isolated pockets of infection. When flu broke out at a Montville construction site, workers banged together a makeshift hospital in hours. By nightfall, 24 patients were being treated.

At least six people died in Uncasville, and the village was left without a practicing physician. Both of its doctors fell ill, and one didn’t survive.

In Stonington Borough, the number of cases overwhelmed the one visiting nurse, who sought volunteer help. The state responded by sending a second nurse.

Forty-seven people died in Stonington, and the town’s major industries were paralyzed by the number of people out sick, nearly 20 percent of the workforce.

Larger towns had it worse. The death toll in Westerly was over 60. Willimantic had 10 in one day and needed volunteers to dig graves.

At least three times in Norwich, ambulances responded to calls only to find the patient already dead. In another case, a woman died the day of her husband’s funeral.

Typical of the regular flu, the 1918 variety generally killed the very old and very young disproportionately. Atypically, it also claimed many who were healthy and in their prime, turning the usual U-shaped mortality curve into more of a W.

In Connecticut, the impact on the young was more extreme, with the majority of deaths, nearly 60 percent, in the 20-40 age range.

“Passing lightly the very young and almost ignoring the old, it aimed straight at the very flower of the flock,” said a 1919 report in the Connecticut Health Bulletin.

The symptoms were ghastly compared to annual outbreaks of aches and fever. The onset was sudden, leaving victims prostrate in an hour or two. Fevers as high as 105 were accompanied by chills, bloody fluid in the lungs, labored breathing and muscle and joint pain.

When a sufferer’s ears, lips and face turned ashen, death was likely, even more so when the face turned purple.

The Journal of the American Medical Association described the experience bluntly: “The patient feels as though he had been beaten all over with a club.”

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With the mayor out of town, Alderman Henry C. Chappell found himself presiding over a city in crisis. On Sept. 25, his first order as acting mayor of New London was a big one: He closed all schools, theaters, churches, dance halls, bowling alleys and anywhere else people gathered indoors.

The flu already had invaded the schools and was attacking roomfuls of students at a time. It soon claimed the life of Marion Ritchie, the Winthrop School principal.

Hundreds packed the city’s four theaters nightly, and when they closed, New London effectively shut down.

“The city will indeed be a lonesome town with all the bright lights dimmed for an uncertain period of time,” The Day said.

Signs of crisis were everywhere. Yellow quarantine flags flew outside the armory on Washington Street, which served as an overflow hospital. A quarter of the operators at Southern New England Telephone were home in bed. The City Council held a meeting outside to keep germs from spreading. The trolley company struggled to keep cars on a schedule with 50 percent of workers out sick.

By October it was clear New London was woefully unprepared. The war had taken one of its hospitals out of service, many nurses were overseas, and doctors were swamped.

“I do not want to say that the seriousness of the situation was not appreciated until the disease ... was in danger of getting out of control,” wrote Theodore Bodenwein, publisher of The Day. But he still upbraided southeastern Connecticut for its listless response.

Charities needed to help those with no access to medical care, he wrote. Volunteers must assist the doctors. The lack of action “doesn’t speak very well for the resourcefulness of the community nor for its spirit of humanity.”

Then things started happening. An emergency hospital opened in the parish house of the First Congregational Church. Patients included a family of six and another of eight. Automobiles were offered to help doctors make their rounds. Volunteers brought food and medicine to the sick.

Morton F. Plant, the millionaire summer resident of Groton, sent word that officials could go to his Griswold Hotel, which was closed for the season, and help themselves to beds and anything they needed.

The epidemic finally peaked and was mostly played out by the end of October. But the third wave soon followed and brought hundreds of new cases and a handful of deaths in late 1918 and early 1919. The victims included Plant, who died at his home in New York. The fourth wave, a year later, was mostly inconsequential.

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Although it’s strangely absent from the national memory, the 1918 flu killed an estimated 500,000 Americans. That’s in the same neighborhood as the Civil War’s death toll.

In Connecticut, about 8,500 died of flu or pneumonia during just the second wave. This included 51 in Groton, 223 in Norwich and a total for southeastern Connecticut probably over 600.

The number of record for New London is 235, or 9.1 of every 1,000 residents. But that doesn’t include the Naval Hospital, which didn’t report to civilian record-keepers. More than 30 flu-related deaths are known to have occurred there.

Whatever the overall number, the 1918 flu easily surpassed what was till then New London’s deadliest health crisis: the yellow fever epidemic of 1798, which killed 81.

A report from Yale University lists factors associated with the hardest-hit Connecticut towns: urban and manufacturing centers; the presence of military men, war workers and Italians, who died in huge numbers; proximity to the railroad; and being struck earlier in the outbreak rather than later.

New London could check every box.

j.ruddy@theday.com