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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.
Human neurons are so small that they require a microscope in order to be seen. However, some neurons can be up to 3 feet long, such as those that extend from the spinal cord to the toes.
The tallest man ever known was Robert Wadlow, an American, who reached the height of 8 feet 11 inches. He died at age 26 years from an infection caused by the immense weight of his body (491 pounds) and the stress on his leg bones and muscles.
The Babylonians wrote numbers in a system that used 60 as the base value rather than the number 10. They did not have a symbol for "zero."
Not getting enough sleep can greatly weaken the immune system. Lack of sleep makes you more likely to catch a cold, or more difficult to fight off an infection.