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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.
Patients who have undergone chemotherapy for the treatment of cancer often complain of a lack of mental focus; memory loss; and a general diminution in abilities such as multitasking, attention span, and general mental agility.
The most destructive flu epidemic of all times in recorded history occurred in 1918, with approximately 20 million deaths worldwide.
Cytomegalovirus affects nearly the same amount of newborns every year as Down syndrome.
Though the United States has largely rejected the metric system, it is used for currency, as in 100 pennies = 1 dollar. Previously, the British currency system was used, with measurements such as 12 pence to the shilling, and 20 shillings to the pound.