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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.
In the ancient and medieval periods, dysentery killed about ? of all babies before they reach 12 months of age. The disease was transferred through contaminated drinking water, because there was no way to adequately dispose of sewage, which contaminated the water.
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.
Thyroid conditions may make getting pregnant impossible.
More than 2,500 barbiturates have been synthesized. At the height of their popularity, about 50 were marketed for human use.