Some scientists warn that global warming could lead to a spread of disease, as the range of where mosquitoes, ticks, mice and other carriers of disease can live expands.
In the United States, people are protected by good sanitation, medicine and wealth. But it's worth remembering that Americans were once terrorized by diseases associated with hot weather. In the 18th and 19th centuries, yellow fever killed more than 100,000 Americans.
The sweltering port cities of Philadelphia, New York and New Orleans all experienced major outbreaks. But the worst swept through Memphis, Tenn., like a biblical plague.
In 1878, people in Memphis began reporting strange weather. It was hot that year, and it got hot early.
"There were newspaper articles and personal accounts that the flowers had bloomed in January and February. They, by March, were already having 80-degree temperatures," says Molly Caldwell Crosby, author of The American Plague, a history of yellow fever.
"It's a very ugly disease — things like eyes bleeding, nose, ears, some pretty gruesome symptoms," Crosby says. "But then it also causes internal bleeding. And one of the telltale signs of yellow fever is what they call 'black vomit.' It's from digesting internal bleeding."
Victims' skin and the whites of their eyes turned yellow. "One New Orleans doctor performing an autopsy that summer described it as bright canary yellow," according to Crosby.
There had been yellow fever epidemics in Memphis before, but never anything like the outbreak in 1878.
Back then, Memphis was a busy trade route for the steamboats that went up and down the Mississippi River.
Visiting a neighborhood of old brick buildings close to the water, Crosby explains, "This would have been ground zero for the outbreak of yellow fever. It was right along the shore of the Mississippi River. There was a lot of poverty. They did have sanitation problems."
The Memphis board of health officially reported the first case on Aug. 14, 1878: a woman who ran a snack shop. News of her death set off mass panic.
"Within hours, the woman's body was burned (and) her building was closed off," Crosby says. During the next three days, between 20,000 and 25,000 people left the city.
More than half of the city's population eventually fled. People left front doors wide open and their silverware set on dining room tables.
Those who stayed behind were largely poor. Many were immigrants; many were black. Of 19,000 people who stayed, 17,000 got sick. More than 5,000 died.
Martyred Caregivers
One who stayed behind was Sister Constance at St. Mary's Episcopal Cathedral. She went from house to house to care for the sick. Sometimes she found abandoned children amid the rotting corpses of their parents.
People thought the disease was spread by bad air. So, even though temperatures were close to 100 degrees that summer, they boarded up their windows and kept fires burning to ward off the outside air.
When people died, their clothing and even their beds were dragged into the streets and burned — because it was thought that would keep the disease from spreading.
After just a few weeks, Sister Constance started to shake and her own skin turned hot to the touch. She knew what that meant. Crosby writes that when the other sisters made up their best mattresses with fresh linens, Sister Constance said no — and took a cot instead.
"She was sick for several days. The night before she died, she said to her nurse, 'I shall never get up from my bed,' Crosby says. "Her last words were: 'Alleluia, Hosannah.' Praise be to God."
Today, those words are engraved in the altar at St. Mary's. Also engraved are the names of the six nuns and priests who died caring for the sick. They're now celebrated as martyred saints by the Episcopal Church.
Elizabeth Wirls works at St. Mary's. "You really do feel their presence," she says of the saints. "It's like they're calling to you. You can do more. It's about ... being called to do for others, not picking and choosing who you do it for."
The nuns and priests are buried at Elmwood Cemetery. Every time a yellow fever victim was buried, the cemetery-keeper's young daughter, Grace, would ring the cemetery's heavy bell — until she came down with the fever, too.
Praying for Respite
The worst of the epidemic lasted for six weeks. Crosby writes that often the only people who dared go out on the streets were the collectors of the dead. With horse and wagon, they shouted "Bring out your dead!" They took the bodies to this cemetery for a hasty burial.
"We are standing over 1,400 bodies, right here," Crosby says, standing in Elmwood Cemetery. "This was a large, mass grave. The grave diggers were burying over 50 people a day, and sometimes only six inches beneath the soil. They didn't have time to dig a full 6 feet. They believed at that time that the corpses could also be spreading disease, so they were trying to get them under the ground as quickly as possible."
The names of the dead were written in ink in leather-bound ledgers. People waited anxiously for fall and the first frost. From experience, they knew that the deaths would stop then, but in 1878, they had no idea why.
It would be another two decades before it was widely understood that yellow fever is spread through the bite of a mosquito, and that the infected insects were stowed away on shipments from Africa that went through the Caribbean and then onto boats to New Orleans and up the Mississippi.
Mosquitoes' Modern Threat
Today, Memphis is still a transit hub — for airplanes, trains and — just like in the 1800s — boats.
On a bluff above the wide Mississippi River, Crosby says, "We're looking over toward President's Island. That's where a lot of the ships came through. The John D. Porter, the Golden Crown — a number of the boats that came through that landed feverish people in Memphis."
Because of the warm weather in 1878, this city had two or three times as many mosquitoes as usual.
They bit someone who was already infected, then bit somebody else — and the disease kept spreading.
Today, yellow fever is no longer much of a threat in this country. There's a vaccine, modern sewer systems and ways to control mosquitoes.
But 25 years ago, a scientist working at another Memphis cemetery, just down the street from the one with all the graves of yellow fever victims, checked a trap and discovered the first Asian tiger mosquito found in the United States. That mosquito spreads another illness: West Nile virus.
Some scientists blame global warming for the tiger mosquito's spread to 26 states and as far north as Illinois. But those first mosquitoes got to the United States the same way as the ones that brought yellow fever — by breeding in pools of water, on boats that made their way across the oceans.
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