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Asthma is the most common chronic childhood disease in the world. Most children who develop asthma have symptoms before they are 5 years old.
The Romans did not use numerals to indicate fractions but instead used words to indicate parts of a whole.
Only 12 hours after an egg cell is fertilized by a sperm cell, the egg cell starts to divide. As it continues to divide, it moves along the fallopian tube toward the uterus at about 1 inch per day.
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.
Before a vaccine is licensed in the USA, the Food and Drug Administration (FDA) reviews it for safety and effectiveness. The CDC then reviews all studies again, as well as the American Academy of Pediatrics and the American Academy of Family Physicians. Every lot of vaccine is tested before administration to the public, and the FDA regularly inspects vaccine manufacturers' facilities.