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For about 100 years, scientists thought that peptic ulcers were caused by stress, spicy food, and alcohol. Later, researchers added stomach acid to the list of causes and began treating ulcers with antacids. Now it is known that peptic ulcers are predominantly caused by Helicobacter pylori, a spiral-shaped bacterium that normally exist in the stomach.
More than nineteen million Americans carry the factor V gene that causes blood clots, pulmonary embolism, and heart disease.
In the United States, an estimated 50 million unnecessary antibiotics are prescribed for viral respiratory infections.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
Multiple experimental evidences have confirmed that at the molecular level, cancer is caused by lesions in cellular DNA.