When the Army Went After Mosquito-Borne Disease

A viral infection transmitted by mosquitoes and linked to travelers from tropical and subtropical climates goes epidemic. There is no known cure. While the medical community debates how to prevent the disease’s transmission, government officials struggle to decide what policies will best serve the public interest. Sound familiar? Welcome to the 19th century, when yellow fever, a relative of the Zika virus, was one of the deadliest of the diseases that army doctors and volunteer nurses battled—and contracted—during the Civil War.

Today the Zika virus is in the news largely because of its suspected link to a serious birth defect. Yellow fever was—and is—a different story. In the 19th century, people feared yellow fever for the rapidity with which it spread and its high death rate: an outbreak in New Orleans in 1853 claimed 28% of the city’s population. Even today, between 20 and 50% of people who develop a severe case of yellow fever die. There is no known cure.

We now know that mosquitoes carry the yellow fever virus from one human to another. In the mid-19th century, doctors did not know how the disease was spread. Many doctors believed yellow fever was transmitted through direct contact with those already infected, so they attributed the annual epidemics that afflicted the coastal south to the arrival of infected seamen on ships from topical ports. Others believed that yellow fever was the result of “miasmas”—foul odors resulting from vegetable and animal waste—or was endemic to warm climates.

One thing everyone who studied the disease agreed on was that newcomers were more apt to contract the disease than those born in areas where yellow fever outbreaks were an annual event. When the Civil War began, Southerners hoped “Yellow Jack” would fight alongside Johnny Reb, killing Yankee soldiers who lacked a natural tolerance for the disease.

Union troops did suffer through several epidemics during the war, mostly in the port cities of North Carolina’s Outer Banks, where Confederate blockade-runners carried infected mosquitoes past the Union navy along with guns and food. But the most interesting yellow fever incident in the war, at least from the public health point of view, was the epidemic that did not happen.

Union forces under the command of General Benjamin “Beast” Butler took possession of New Orleans in April 1862. Because of its strong commercial ties to Latin America and the Caribbean, where yellow fever was endemic, the city was the yellow fever center of the South, suffering from annual epidemics throughout the the 1840s and 1850s. Soon after his arrival, Butler heard rumors that not only were the city’s residents counting on yellow fever to clear out the Union troops, but congregations of New Orleans churches were actively praying for the pestilence to arrive.

Determined to lessen the impact of the predicted epidemic, Butler read medical studies on yellow fever and consulted with local doctors about the etiology of the disease. He came to a conclusion that combined two popular theories regarding the spread of yellow fever: that the disease was spread through the miasma caused by rotting vegetable and animal matter but that the original poison that caused it was imported from the tropics. (Pasteur’s germ theory of disease was still several years away.) Consequently, he reasoned, preventing an outbreak of the disease required an aggressive two-pronged strategy of quarantine and sanitation.

Butler ordered all incoming ships to stop 70 miles below New Orleans, where a medical officer inspected them. Any ship with infectious disease on board was held in quarantine for 40 days and then re-inspected. Ships arriving from ports where yellow fever was endemic were quarantined for the same period whether or not their crews or passengers showed signs of disease. Ships that attempted to sail upriver without medical clearance found Butler was prepared to enforce his quarantine rules with cannon fire. As an additional precaution, Butler threatened any inspecting doctor who knowingly allowed an infected ship to sail into New Orleans with the death penalty.

With his quarantine system in place, Butler began a massive cleanup campaign in New Orleans. Two thousand men worked for 30 days to clean waste from the public streets, squares and vacant land. Invoking martial law, Butler ordered residents to clean their homes and yards to the satisfaction of military inspectors and initiated a system of refuse collection. If individuals refused to cooperate, they faced a stay in the parish prison. New Orleans had never been so clean.

Butler’s attempt to stop the spread of a disease whose true cause was unknown was surprisingly successful, perhaps because his rigid quarantine restrictions kept infected mosquitoes from reaching the city. The feared epidemic did not materialize. During the first year of Union occupation, only two deaths from yellow fever were recorded in New Orleans. When General Nathanial Banks replaced Butler in November 1862, he continued Butler’s policies, with equal success.

Butler’s tactics were not new. New Orleans had tried both quarantine and cleanup in the past. But Butler had the force of martial law behind his edicts. As soon as civil authorities took over the administration of public health measures at the end of the war—without the threat of cannon shot or arbitrary imprisonment to help enforce them—yellow fever and other infectious diseases struck the city once more in epidemic force. It would be another 40 years before a peacetime government would be prepared to train the big guns on yellow fever. When a major epidemic swept the city in 1905, the federal government declared war on mosquitoes—and won.

Historians explain how the past informs the present

Pamela D. Toler is the author of Heroines of Mercy Street: The Real Nurses of the Civil War.