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More than 2,500 barbiturates have been synthesized. At the height of their popularity, about 50 were marketed for human use.
Pubic lice (crabs) are usually spread through sexual contact. You cannot catch them by using a public toilet.
Giardia is one of the most common intestinal parasites worldwide, and infects up to 20% of the world population, mostly in poorer countries with inadequate sanitation. Infections are most common in children, though chronic Giardia is more common in adults.
Astigmatism is the most common vision problem. It may accompany nearsightedness or farsightedness. It is usually caused by an irregularly shaped cornea, but sometimes it is the result of an irregularly shaped lens. Either type can be corrected by eyeglasses, contact lenses, or refractive surgery.
There are approximately 3 million unintended pregnancies in the United States each year.
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