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Did you know?
Vaccines prevent between 2.5 and 4 million deaths every year.
Did you know?
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.
Did you know?
Normal urine is sterile. It contains fluids, salts, and waste products. It is free of bacteria, viruses, and fungi.
Did you know?
There are more bacteria in your mouth than there are people in the world.
Did you know?
Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.