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The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
The most destructive flu epidemic of all times in recorded history occurred in 1918, with approximately 20 million deaths worldwide.
Calcitonin is a naturally occurring hormone. In women who are at least 5 years beyond menopause, it slows bone loss and increases spinal bone density.
A cataract is a clouding of the eyes' natural lens. As we age, some clouding of the lens may occur. The first sign of a cataract is usually blurry vision. Although glasses and other visual aids may at first help a person with cataracts, surgery may become inevitable. Cataract surgery is very successful in restoring vision, and it is the most frequently performed surgery in the United States.
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.