“moschetoes Were Uncommonly Numerous”

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Thus reasoned the fiery minister of the Lutheran congregation who, it should be pointed out, did not limit himself to castigating his city. Unflinchingly he stood by it in this time of distress, nursing its sick and burying its dead.

The air of mystery which surrounded the epidemic added greatly to the general sense of frustration. The physicians, who at this period knew nothing of germs and viruses, groped in the dark. They did not know how the fever spread from person to person, nor could they fathom its material basis. True, they spoke of “miasmata,” theoretical poisonous particles supposedly floating in the air, as the cause of the fever, all the while well aware that they were treading on very infirm ground. They had no dear concept of the nature of these miasmata—whose very existence was, in fact, open to doubt.

In their uncertainty the doctors regarded many things as being connected with the fever. “Moschetoes (the usual attendants of a sickly autumn) were uncommonly numerous,” commented Dr. Rush. His observation was pregnant with future promise to which he, however, obviously attached no greater significance than to the irrelevant fact, recorded in the very next sentence, that an occasional dead cat had added to the “impurity of the streets.”

Since no one then really knew anything about the nature of yellow fever it is not astonishing that all attempts to halt the epidemic failed. Apparently the disease would have to run its course, uninfluenced by human measures, until terminated by the onset of rain and cold. All hope was placed on this contingency. But the weather continued to be fine and “the light of the morning mocked the hopes that were raised by a cloudy sky in the evening. The sun ceased to be viewed with pleasure.”

Then, suddenly, towards the end of October, the epidemic broke. The death rate dropped precipitously. There had been hardly any rain and the weather had been as warm as during the most fatal period. Again the unexpected had happened. Once more the disease had taken-an inexplicable turn. Its end had come as mysteriously as had its onset and both were as little comprehensible as was the course it had taken. “Human wisdom and calculation,” wrote Mathew Carey, the most important lay chronicler of the epidemic, had been “set … at defiance.”

People began coming back to Philadelphia. Houses and stores were reopened. Vehicles again appeared on the streets; pedestrians once more went about their business. December 12 was designated as a day of thanksgiving. The city took on its normal appearance.

The ravages had been dreadful. More than 4,000 persons had succumbed in a period of three months. Few persons were spared the loss of dear ones. Many children had become orphans; many parents childless. The epidemic was long remembered.

But it was not to be the last great outbreak of yellow fever in the United States. Two years later there was a serious epidemic in New York; five years later Philadelphia was once again in its grip. In the following century the same pattern prevailed. Smaller and greater outbreaks followed one another in rapid succession. Especially the South was hard hit, but seaport towns as far north as Boston and Halifax were not spared. New Orleans, Savannah, Charleston, and Baltimore bore the brunt. Nearly 8,000 persons perished in New Orleans in 1853; 13,000 died from yellow fever in the Mississippi Valley in 1878.

In the second half of the Nineteenth Century, with the researches of Pasteur and Koch, great advances were made in the recognition of infectious diseases. Yellow fever remained an enigma. At last, in 1900, more than 100 years after the great Philadelphia epidemic, Major Walter Reed of the U.S. Army Medical Corps, following a lead of the Cuban physician, Dr. Carlos Finlay, demonstrated that yellow fever is transmitted from man to man by the bite of the mosquito known as Aëdes aegypti . The way to the conquest of this terrible scourge had been opened. An extensive program of mosquito extermination brought the disease under control. And with the isolation of the virus causing yellow fever, three decades later, it became possible to produce an effective anti-yellow-fever vaccine.

No one remembered that on August 29, 1793, there had appeared an anonymous letter in the Philadelphia American Daily Advertiser , describing a simple and cheap method of destroying mosquitoes, “those poisonous insects … so distressing to the sick, and troublesome to those who are well.” A little oil poured into cisterns and rain-water casks, the breeding places of mosquitoes, would kill the “whole brood.”

In the excitement of those dreadful days the letter went unnoticed. Philadelphians had more important things to do than rid themselves of a nuisance. How different might the fate of their city have been had they paid more attention to ”… the usual attendants of a sickly autumn.” Dr. Laurence Farmer is a physician with special interest in the history of medicine. His recent book, Doctors’ Legacy (Harper), is a collection of physicians’ letters during the last two and a half centuries.