Yellow Fever

Photo: CDC, Public Domain

Yellow fever was one of the great health scourges of the late 18th and early 19th centuries. Typically a tropical disease, it struck in sporadic epidemics with devasting effects in temperate northern climates.

Little was known at the time about the cause of the disease, except that it usually broke out near the waterfront of a large port. It was widely believed it was airborne, or “miasmatic” of the poorly drained and swampy lands which produced unhealthy conditions.

The illness ranged from a fever with aches and pains to severe liver disease with bleeding and jaundice (yellow) skin. Mortality rates could be incredibly high, often reaching 50 percent. The most horrible of all yellow fever epidemics in North America occurred in 1793 in Philadelphia when over 5,000 perished. Another 20,000 citizens fled the city.

Yellow fever would be one of several ailments that would worry the Captains, simply because of the many marshy areas they encountered along the Trail. But due to common beliefs of the time, they were only concerned about the quality of the air, not the mosquitoes that also thrived in such environments. Meriwether Lewis wrote about the huge number of mosquitoes in the area of the “council bluff” where they met the Otoes and Missouris. Then he added “The air is pure and helthy So far as we can judge.”

No documented cases of yellow fever were mentioned in the journals, although there are numerous entries about men have the “argue” or “bilious fevers.”

It wouldn’t be until 1881 when Carlos Finlay first proposed that the mosquito was responsible for spreading yellow fever. There is still no known cure, but a safe and effective vaccine is available. Unfortunately, yellow fever still accounts for hundreds of deaths each year, primarily in South American and African nations.