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About one in five American adults and teenagers have had a genital herpes infection—and most of them don't know it. People with genital herpes have at least twice the risk of becoming infected with HIV if exposed to it than those people who do not have genital herpes.
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.
The familiar sounds of your heart are made by the heart's valves as they open and close.
The most destructive flu epidemic of all times in recorded history occurred in 1918, with approximately 20 million deaths worldwide.
The lipid bilayer is made of phospholipids. They are arranged in a double layer because one of their ends is attracted to water while the other is repelled by water.