My dear Julia,

The fever has assumed a most alarming appearance … In one house I lost two patients last night, a respectable young merchant and his only child. His wife is frantic this evening with grief … Five other persons died … yesterday … and four more last night …

... your sincere and affectionate

BENJN RUSH

In summer 1793, a malignant visitation spread over the nation’s capital, carrying off young and old, poor and prosperous in agonizing ways.

People collapsed in the streets untended and died horrible deaths at home, their skin turning yellow, their vomit dark with blood.

Families were wiped out. Handshaking stopped. Citizens avoided one another and covered their faces with cloth.

Half the residents fled the city, including President George Washington. Schools were closed. Some roads outside town were guarded to keep refugees away.

This was Philadelphia, the U.S. capital from 1790 to 1800. Wagons arriving from the city were burned as a precaution. Letters and newspapers from Philadelphia were handled with tongs.

During the worst of it, a hundred people were buried a day. Historian J.H. Powell’s classic 1949 account is entitled “Bring Out Your Dead,” after the calls of the roving burial teams.

What was destroying them, scientists say, was the first virus found to cause human disease.

It was yellow fever. In Philadelphia that year, it killed roughly 5,000 people, about one-tenth of the population. (The deaths of one-tenth of Washington’s population today would mean a toll of 70,000 people.)

Thousands more were infected but either had no symptoms or only a mild version of the disease, said J. Erin Staples, head of a surveillance and epidemiology team at the Centers for Disease Control and Prevention.

“For every death, there’s about 21 other infections,” she said modeling showed. So most of Philadelphia’s 50,000 people probably were infected. “They were either lucky that they didn’t develop disease or had mild disease compared to those that were unlucky and died.”

Yellow fever is one of more than 200 known human viruses, according to the National Institutes of Health. They include those that cause HIV/AIDS, Ebola, polio, smallpox, measles, mumps, rabies, the common cold and now the novel coronavirus.

In the late 1800s, scientists were just starting to realize that strange microbes smaller than bacteria were causing disorders in plants and animals. Bacteria, which had been discovered in the 1670s, had been associated with human illnesses such as typhoid fever, cholera and tuberculosis.

At first, yellow fever was thought to be caused by bacteria, too. But that theory was discounted when famous U.S. Army physician Walter Reed reported in 1900 that the leading suspect bacteria was not found in the blood of fever cases he studied in Cuba.

There was an alien “parasite” at work, he believed.

“At the time they didn’t even call it a virus,” Staples said. “They didn’t know really what a virus was.”

Yellow fever, in the worst cases, attacks the liver, inhibiting the ability of blood to clot. That can cause bleeding in the stomach and the dark vomit, Staples said. “People were also described as having blood coming from other places … out of different orifices,” she said.

The liver damage also turned the skin yellow and gave the disease its name.

None of this was known in Philadelphia in 1793.

The cause of the “bilious remitting Yellow Fever” was thought to be a load of rotting coffee left on a wharf on the Delaware River, “corrupting” the air.

So believed Benjamin Rush, the prominent 47-year-old Philadelphia physician, civic leader and signer of the Declaration of Independence. (A statue of him stands in the District’s Foggy Bottom neighborhood, unveiled in 1904 and funded by the American Medical Association.)

Rush’s theories about the origin of the illness were misguided, and his treatments — chiefly massive blood letting — were dangerous. He also advertised “Doctor Rush’s Mercurial Sweating Powder for Yellow Fever.”

But he valiantly remained in the city. He was at forefront of the fight against the epidemic and may have had the fever himself. And, to the benefit of history, he wrote almost daily to his wife, Julia, who was staying away in New Jersey.

“Dejection sits upon every countenance,” he wrote her Aug. 26. “Five persons died this morning … and five more are expected to die tonight.”

To cleanse the infected midsummer air, residents lighted bonfires nightly on street corners and shot off guns and cannons. Women and children began smoking cigars. Garlic was chewed or carried in the pockets or shoes.

A layer of fresh dirt spread on the floor of a house was said to block the illness.

Those who went outside wore the equivalent of surgical masks — handkerchiefs soaked in vinegar or camphor — or carried tarred rope.

The homes of the sick were marked so that passersby could avoid them.

Some rejected the nature of the disease. Rush wrote that a rival physician, James Hutchinson, “denied the existence of a contagious fever … [and] treated the report of it with contempt and ridicule.” Hutchinson died Sept. 6, Rush wrote.

(Hutchinson was right. The fever wasn’t contagious, as the coronavirus is. It was carried by mosquitoes.)

Business collapsed. Stores closed. One newspaper — the Federal Gazette — kept publishing.

The fever claimed Rush’s sister, Rebecca. “My heart has flown into the coffin with her,” he wrote.

Rush told his wife to not even speak to anyone from Philadelphia, as the city had become a “mass of contagion.” A Philadelphia man named Christian Piercy got sick on a stagecoach in New Jersey and was thrown off.

A woman named Dolley Todd lost her husband, her infant son, her father-in-law and her mother-in-law. She also was infected, but she would survive and later become first lady, as the wife of President James Madison.

On one street, 38 victims from 11 families died in nine days, Rush wrote. In one family, 11 people died.

“It is painful to look back on what we have seen, but more distressing to look forward,” Rush wrote on Sept. 1. “I fear we have seen only the beginning of the awful visitation.”

A desperate appeal was made to the city’s African Americans, who were erroneously thought to be immune.

“Happy would it have been for you, and much more so for us, had this observation been verified by our experience,” Richard Allen, founder of the African Methodist Episcopal Church, and abolitionist Absalom Jones wrote later.

They responded anyway, died in droves and ministered how they could. Often they were too late to do much. Many people they checked on were already dead.

“We found them in various situations,” the two formerly enslaved ministers recalled of their home visits. “Some laying on the floor as bloody as if they had been dipt in it … others laying on a bed with their clothes on as if they had come in fatigued and lain down to rest. Some appeared as if they had fallen dead on the floor.”

“Truly, our task was hard, but through mercy, we were able to go on,” they wrote.

A century later, doctors suspected that mosquitoes were transmitting yellow fever from person to person. But the virus was still killing people — including scientists researching it — and making people sick. And no one knew the nature of the microbe doing the damage.

In 1900, Reed set up what he called an “experimental sanitary station” in Cuba, where yellow fever was prevalent. He named it Camp Lazear, for Jesse W. Lazear, a medical colleague who had died of the fever that year.

After extensive testing on volunteer patients who were infected, Reed confirmed that mosquitoes were the carrier and eliminated bacteria as a cause.

“No body, bacterial or protozoan, which could be brought into view [under the microscope] was present in the blood of these cases,” he wrote in 1902.

The “specific agent of yellow fever [was] … a micro-organism so minute in size that it might be designated as ultra-microscopic,” he wrote.

The yellow fever virus was isolated in 1927, and scientists soon came up with an effective vaccine, called 17D, a weakened form of the virus itself. It’s still in use, and a recent scholarly paper called it “one of the most outstanding human vaccines ever developed.”

But in Philadelphia in 1793, the only remedy would be something that killed mosquitoes.

As summer turned to a warm fall, the epidemic went on. On Oct. 9 there were 102 burials. Cemeteries looked like plowed fields because there were so many burials, an observer said.

On Oct. 11, there were 119.

But gradually the fever burned itself out. People developed immunity. And the days were getting cooler.

On Oct. 20, there were only 55 burials. Seven days later there were 13.

And on the morning of Oct. 28, the ground was covered with frost.

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