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Cancer has been around as long as humankind, but only in the second half of the twentieth century did the number of cancer cases explode.
The horizontal fraction bar was introduced by the Arabs.
Vaccines cause herd immunity. If the majority of people in a community have been vaccinated against a disease, an unvaccinated person is less likely to get the disease since others are less likely to become sick from it and spread the disease.
The average human gut is home to perhaps 500 to 1,000 different species of bacteria.
Many people have small pouches in their colons that bulge outward through weak spots. Each pouch is called a diverticulum. About 10% of Americans older than age 40 years have diverticulosis, which, when the pouches become infected or inflamed, is called diverticulitis. The main cause of diverticular disease is a low-fiber diet.