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The most destructive flu epidemic of all times in recorded history occurred in 1918, with approximately 20 million deaths worldwide.
About 3.2 billion people, nearly half the world population, are at risk for malaria. In 2015, there are about 214 million malaria cases and an estimated 438,000 malaria deaths.
When blood is deoxygenated and flowing back to the heart through the veins, it is dark reddish-blue in color. Blood in the arteries that is oxygenated and flowing out to the body is bright red. Whereas arterial blood comes out in spurts, venous blood flows.
Increased intake of vitamin D has been shown to reduce fractures up to 25% in older people.
The heart is located in the center of the chest, with part of it tipped slightly so that it taps against the left side of the chest.