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The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
A seasonal flu vaccine is the best way to reduce the chances you will get seasonal influenza and spread it to others.
The familiar sounds of your heart are made by the heart's valves as they open and close.
Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
Today, nearly 8 out of 10 pregnant women living with HIV (about 1.1 million), receive antiretrovirals.
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