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Yellow fever is one of the deadliest diseases known to man. It’s also a great example of how our beliefs can shape our understanding of health and disease. Yellow fever is caused by a virus that infects only certain kinds of mammals—most notably, primates like monkeys and apes, but also some other kinds of small-bodied mammals like bats, rodents, and carnivores that come into contact with them. Once an infection sets in, there’s no cure—once you contract it, you’ll die within a matter of days or weeks. Thankfully, humans have been developing vaccines against yellow fever for several decades now; even so, we still see cases here and there because the virus occasionally mutates in new hosts (like squirrels) or spreads farther than scientists had anticipated (like through airline travel). The fear of yellow fever has existed since at least the 18th century. That’s when its first outbreaks took place in South America after European colonists brought their livestock with them from Africa. The creatures that were responsible for these outbreaks became known as yellow fever mosquitos because they lived off blood from smaller mammals like mice and rats. In order to keep these mosquitos at bay, many people began living in walled or otherwise isolated settlements called “redouts” or “fence-towns.” These precautions worked well for many years until the disease returned again with a vengeance in 1867 after another outbreak had decimated both European
How the fear of yellow fever has shaped our perception of color
We’ve already seen how the fear of yellow fever caused people to associate it with dark, foreboding tones—darker, even. But did you know that this association has also influenced our perception of color in other ways, too? When scientists first began examining the relationship between yellow fever outbreaks and the color yellow, they noticed that people living in yellow fever-infected regions tended to associate the color yellow with darkness, danger, and foreboding tones. What was even more interesting was that this association only applied to certain hues of yellow—not the brighter, more saturated shades that we associate with the color today. In fact, scientists didn’t start associating yellow with disease until the 18th century, right around the same time that yellow fever outbreaks were becoming more and more common. So it seems as though yellow fever had something to do with shaping our perception of the color yellow.
Why do we see white as the color of safety and purity?
As we just saw, yellow fever has been associated with dark, foreboding tones for at least a few hundred years. So why do we associate white with safety and purity? It’s not like white is actually a pure color—it’s actually an in-between color that falls between black and a variety of shades of gray (nothing is 100% pure white). White is also the color of snow, which is a substance that’s inherently pure and clean, nothing more. So why then do we associate white with safety? One possible explanation is that white makes something more visible. This could help to explain why white is often associated with safety, because it could help to make something like a fire or a dangerous disease more obvious. Another possible explanation is that white is actually a very strong contrast to almost all other colors. This means that it can stand out even more if it’s used alongside a contrasting shade of black. This combination of contrasting colors and the contrasting contrast between the color white and black can help to visually stand out safety messages.
Yellow fever: a disease caused by a virus that infects only certain kinds of mammals
Yellow fever isn’t actually yellow at all; it’s actually a mix of yellow and brown. This brownish color is caused by the virus itself, which contains a protein called falciparum that causes it to turn brown when it’s exposed to air. Yellow fever is a disease only found in certain kinds of mammals who can then transmit it to humans. The mosquitoes that spread yellow fever are only found in certain parts of Africa, South America, and Southeast Asia. After these regions, the virus is extremely rare. It was once thought that humans could get yellow fever from any kind of mosquito, but it’s now known that humans can only get infected with yellow fever from a specific kind of mosquito known as the Aedes aegypti mosquito. Humans can’t transmit yellow fever to other mammals, and they can’t get yellow fever from mosquito bites.
The truth about how you get yellow fever: How mosquitoes actually transmit it
Before we get into the details of how yellow fever is transmitted, let’s go over the basics of how yellow fever is actually caused. After a mosquito feeds on a person who’s already infected with yellow fever, the virus is shed in the mosquito’s saliva. This saliva is then used to bite other mosquitoes—who pass on the virus to the humans who they bite. This yellow fever virus can only infect certain kinds of mammals, and they can only transmit it to people if they’re bitten by a specific kind of mosquito who can pass it on to humans. Now let’s get into the details of how mosquitoes actually spread yellow fever. Aedes mosquitoes are the kind that can spread yellow fever. They’re especially bad in tropical, humid climates. Yellow fever is most common in South America and Southeast Asia because these two regions have a lot of Aedes aegypti mosquitoes. Before the disease can infect humans, mosquitoes must pick up the virus in the same way as we just saw—by feeding on infected mammals like rodents and bats who have already been bitten by Ae. aegypti mosquitoes who have picked up the virus in the same way.
The final word on why we tend to associate yellow with sickness
Yellow fever is a disease caused by a virus only found in certain kinds of mammals. It’s only transmitted from mammals to people by a specific kind of mosquito. It causes a dark, foreboding tone in the things that it infects. After all of these facts about the real-life yellow fever, what’s left for you to conclude? Yellow fever is a disease only found in certain kinds of mammals who can then transmit it to people.