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HIV testing reach is still limited. An estimated 40% of people with HIV (more than 14 million) remain undiagnosed and do not know their infection status.
Autoimmune diseases occur when the immune system destroys its own healthy tissues. When this occurs, white blood cells cannot distinguish between pathogens and normal cells.
Urine turns bright yellow if larger than normal amounts of certain substances are consumed; one of these substances is asparagus.
There are 20 feet of blood vessels in each square inch of human skin.
Though the United States has largely rejected the metric system, it is used for currency, as in 100 pennies = 1 dollar. Previously, the British currency system was used, with measurements such as 12 pence to the shilling, and 20 shillings to the pound.