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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.
People about to have surgery must tell their health care providers about all supplements they take.
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.
Before a vaccine is licensed in the USA, the Food and Drug Administration (FDA) reviews it for safety and effectiveness. The CDC then reviews all studies again, as well as the American Academy of Pediatrics and the American Academy of Family Physicians. Every lot of vaccine is tested before administration to the public, and the FDA regularly inspects vaccine manufacturers' facilities.
Blood is approximately twice as thick as water because of the cells and other components found in it.