Yellow Jack was one of the many names for yellow fever. Yellow fever was the scourge of the 18th and 19th centuries in the Western world.
The disease itself is native to sub-Saharan Africa and is carried by aedes aegypti mosquito. It was brought to the Western world on Dutch slave ships, probably sometime in the 1600's. The disease killed hundreds of thousands of people in Western Europe and America, maybe even millions. It could be found in London, Paris, Brussels, New York, Philadelphia and even Boston. One outbreak in Philadelphia in the late 18th century cost the city nearly 20% of its population.
It's known as yellow fever because the second stage brings about jaundice. Most people know that turns your skin yellow. The disease attacks the abdominal organs. It starts out with fever and chills and a monstrous, splitting headache. It comes on suddenly, much like influenza.
The disease has two stages. Most people only went through the first stage and recovered just fine. The second stage is the stage that was deadly and led to the great fear of yellow fever. It was a very painful death that included lots of vomiting and bleeding in the stomach and intestines. Very nasty way to go. It wasn't until 1900 that it was discovered that yellow fever was spread by mosquitoes. We have Drs. Walter Reed and James Carroll to thank for that. And the Spanish-American War.
Yellow fever struck every summer, usually starting up in mid-June and the outbreaks would last until first frost killed the mosquitoes. If you survived the first stage of yellow fever, you were then immune to the disease. But only if you continued to live in an area where yellow fever was a problem. It eventually died out in the north once the slave trade was made illegal, but lived on and on in the South because we don't have really cold winters. It was considered to be a white man's disease. The slaves and their descendants were genetically immune to the disease.
The image of Yellow Jack is courtesy of the University of Virginia Healthcare System. They have an excellent online collection of yellow fever history and a wonderful write-up of how the mosquito theory was confirmed.
I've also been tagged for the middle name meme. However, I have 8 letters in my middle name so I'm going to have to do some thinking on it and will post my answers this weekend.