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Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
Once thought to have neurofibromatosis, Joseph Merrick (also known as "the elephant man") is now, in retrospect, thought by clinical experts to have had Proteus syndrome. This endocrine disease causes continued and abnormal growth of the bones, muscles, skin, and so on and can become completely debilitating with severe deformities occurring anywhere on the body.
Autoimmune diseases occur when the immune system destroys its own healthy tissues. When this occurs, white blood cells cannot distinguish between pathogens and normal cells.
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.
Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.