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When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
The most destructive flu epidemic of all times in recorded history occurred in 1918, with approximately 20 million deaths worldwide.
Pope Sylvester II tried to introduce Arabic numbers into Europe between the years 999 and 1003, but their use did not catch on for a few more centuries, and Roman numerals continued to be the primary number system.
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.
A seasonal flu vaccine is the best way to reduce the chances you will get seasonal influenza and spread it to others.