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The most destructive flu epidemic of all times in recorded history occurred in 1918, with approximately 20 million deaths worldwide.
The horizontal fraction bar was introduced by the Arabs.
The average adult has about 21 square feet of skin.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
There are 20 feet of blood vessels in each square inch of human skin.
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