Leonard Wood | The Eradication of Yellow Fever | Medicine and the Spanish-American War

Trained in scientific medicine. Wood not only understood the magnitude of the problem, but also the rationale and the necessity for redesigned experiments to prove the mosquito hypothesis, and, as military governor, he had the power to make the experiments happen. Wood had good reason to take the risk; eradication of yellow fever had been one of his primary charges, sanitation had failed, and the governor was under withering attack from the American press.

Reed decided to experiment on recently arrived Spanish immigrants, reasoning that they were unlikely to be immune, that they would need the money, and that the reaction if they died would be less than if an American soldier or a Cuban citizen succumbed. Knowing that he might get a reaction from Madrid, Wood approached the consul, Spain's senior representative in Havana, who agreed to let his country's citizens participate provided they were at least twenty-four years old, were volunteers, and were paid.

The Spanish volunteers were offered $100 in gold and immunity certificates that entitled them to wages twice those of a nonimmune. If they got the disease, they were promised $250 and the "best treatment" by American doctors and nurses all though no treatment had any effect on the disease and Reed knew it.

The pay was generous enough to attract the attention of American soldiers who campaigned for the right to participate. They even scattered bones on the path the Spanish volunteers had to walk to reach Reed's office and spread the rumor that they were remains of previous experimental subjects.

On November 20, Reed's team pitched seven tents a mile from the nearest town, quarantined the area, christened it Camp Lazear, and inoculated their first five volunteers, four of whom got yellow fever. Reed then started controlled experiments designed to prove the mosquito hypothesis beyond question. He built two 14 x 20 foot frame houses, each with two tiny, well-screened windows and two similarly screened doors. The buildings were specifically designed to limit sunlight and ventilation which might lessen the risk of infection. Each had a coal stove to keep the temperature over 90 degrees and basins of water to make the rooms drip with humidity.

In Building #1, the "Infected Clothing and Bedding Building," volunteers were locked up for twenty days with clothes, sheets, blankets, and pillows soaked with blood, vomit, and feces ripened for two weeks after having been used by yellow fever patients. The first volunteers retched and staggered out but were eventually able to tolerate the steamy, fetid room, and none got the fever.

Building #2, the "Infected Mosquito Building," was identical in construction to the other except it was divided in half by a screen. All contents of both sides were decontaminated, and fifteen infected mosquitoes were put in one side along with a volunteer who had spent a month in quarantine so there would be no question of prior infection. Two other volunteers were placed in the nonmosquito side. Only the "mosquito side" volunteer got the disease.

Carroll went on to prove he could transmit the disease by injecting infected blood that had been passed through an earthenware filter fine enough to trap any known bacteria. Yellow fever was, without question, caused by a "filterable virus" transmitted by the Stegomyia mosquito. As expected, papers in Havana and the United States excoriated Reed and Wood for the experiments' design, but none questioned the results.

As military governor. Wood was in a unique position to apply Reed's results. Through Kean, he ordered that all barracks be covered with "mosquito bars" and that all standing water around barracks and hospitals be drained. Water barrels were layered with kerosene and had taps put in their bottoms.

Wood extended the order to all Cuba on December 31,1900. Wood's chief medical officer, William Gorgas, was initially skeptical of mosquito control and tried vaccinating volunteers with serum taken from patients with a "light case" of yellow fever. When the vaccinations resulted in several deaths including the highly publicized demise of an American nurse, he joined the mosquito control campaign that brought him worldwide acclaim.

Gorgas redefined disinfection from sanitation to removal of insects and recommended fumigation of infected houses with sulphur, formaldehyde, or insect powder. Since the Stegomyia was known not to fly far, any occurrence of yellow fever in an army facility was taken as prima facie evidence of negligence by the camp commander.

Next, the measures were extended to civilians. Wood ordered district commanders to report all fever cases and to "investigate the prevalence of mosquitoes, their species, the extent to which they produce malaria and yellow fever infections, the measures adopted to prevent their propagation, and the success thereof."

Mayors were notified that the nearest United States Army post surgeon would henceforth be the local medical inspector and would be responsible for mosquito control. It was made a misdemeanor to have mosquito larvae on any premises. Cisterns and water buckets had to be screened or kerosened and army carpenters were supplied to drill taps at the bottom of storage barrels.

Gorgas's sanitary officers divided Havana into twenty districts and inspected every house monthly. Homeowners in violation of mosquito regulations were fined $5, although the fines were returned when the violations were corrected (2450 of 2500 fines were eventually remitted).

By September 1901, yellow fever in Havana had essentially ceased to exist, and mosquito control had almost eradicated malaria as well. From 1898 to 1900, malaria killed 1,047 people in the city each year. In 1901, 151 died; in 1902, there were 77 malaria fatalities; from 1902 to 1912, an average of 44 died each year; and, in 1912, only a single malaria death was recorded in all Havana. There had been 103 yellow fever deaths in Havana in 1899, 310 in the grim 1900 yellow fever year, only eighteen in the first nine months of 1901, and none in the next nine months.

In 1902, the death rate among American soldiers stationed in Cuba was the lowest of any billet in the world and one-third that of men stationed in the United States. By the end of 1900, Havana, which had been one of the world's most dangerous cities, had an infectious disease death rate lower than Dublin, Munich, or Le Havre.

Wood called the conquest of yellow fever "worth the cost of the war, and probably the most important (advance) in the field of medicine since the discovery of vaccination."