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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 immune system needs 9.5 hours of sleep in total darkness to recharge completely.
Prostaglandins were first isolated from human semen in Sweden in the 1930s. They were so named because the researcher thought that they came from the prostate gland. In fact, prostaglandins exist and are synthesized in almost every cell of the body.
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.
Signs of depression include feeling sad most of the time for 2 weeks or longer; loss of interest in things normally enjoyed; lack of energy; sleep and appetite disturbances; weight changes; feelings of hopelessness, helplessness, or worthlessness; an inability to make decisions; and thoughts of death and suicide.