US troops during the Spanish-American War had a lot more to worry about than just enemy soldiers and battlefield injuries. An even bigger threat at the time was yellow fever—a virus that caused flulike symptoms; jaundice (yellowing of the skin, from which the disease gets its name); and, often, internal bleeding, “black vomit,” and death.

The epicenter of yellow fever infections was Cuba, where much of the fighting in the war happened. The disease had been recorded in the Caribbean for the first time in 1596 and was thought to have come over on slave ships from Africa. The disease was known to strike other parts of the continent—an epidemic hit Philadelphia in 1793, causing the government to flee as 10 percent of the city’s population perished—but nowhere else was it as common as in Havana.

The United States temporarily took control of Cuba after winning the war, and in 1900 the US Army Medical Corps appointed the physicians Walter Reed (1851–1902) and James Carroll (1854–1907) to head a commission aimed at eradicating yellow fever. Mosquitoes had long been suspected as the agent of infection, and to test this hypothesis, Reed and Carroll divided soldiers into two groups—one of which lived among the clothing and bedding of yellow fever victims and one of which was kept in isolation but then bitten by mosquitoes. None of the first group fell ill, but 80 percent of the second did.

The next year, the government began a massive effort to eradicate mosquitoes, placing the campaign under the American military doctor William Gorgas (1854–1920). By eliminating any barrel, cistern, or tank where stagnant water could collect and using primitive pesticides—Gorgas poured kerosene into ponds to kill the insects—he managed to annihilate the mosquito population within 3 months, virtually eliminating yellow fever from Havana. Gorgas then targeted Panama, where the French had recently abandoned construction of the Panama Canal because of too many deaths from disease. Americans took over the operation in 1904, and within 2 years the Canal Zone was fever free. Similar programs were carried out, mostly with great success, in Brazil, Guatemala, Honduras, Mexico, Nicaragua, Peru, and El Salvador.

ADDITIONAL FACTS

  1. In 1925 in Africa, a new variety of yellow fever broke out, to which humans and monkeys are susceptible. Because there is no way to eliminate mosquitoes from the jungle, researchers developed a vaccine to fight the epidemic.
  2. Reed remains the youngest student ever to graduate from the University of Virginia School of Medicine, where he completed a 2-year course and earned his degree at age 17. He obtained a second MD degree from New York University (NYU) Bellevue Hospital Medical College in 1870 at age 19.
  3. Gorgas also graduated from the NYU Bellevue Hospital Medical College, in 1879. He went on to become surgeon general of the army and president of the American Medical Association.
  4. Carroll allowed himself to be bitten by a mosquito that had bitten yellow fever victims, and 4 days later he came down with yellow fever. He survived but was left with heart disease, from which he died 17 years later.