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.