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Only one in 10 cancer deaths is caused by the primary tumor. The vast majority of cancer mortality is caused by cells breaking away from the main tumor and metastasizing to other parts of the body, such as the brain, bones, or liver.
As the western states of America were settled, pioneers often had to drink rancid water from ponds and other sources. This often resulted in chronic diarrhea, causing many cases of dehydration and death that could have been avoided if clean water had been available.
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
You should not take more than 1,000 mg of vitamin E per day. Doses above this amount increase the risk of bleeding problems that can lead to a stroke.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.