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Astigmatism is the most common vision problem. It may accompany nearsightedness or farsightedness. It is usually caused by an irregularly shaped cornea, but sometimes it is the result of an irregularly shaped lens. Either type can be corrected by eyeglasses, contact lenses, or refractive surgery.
The longest a person has survived after a heart transplant is 24 years.
Cyanide works by making the human body unable to use oxygen.
More than 50% of American adults have oral herpes, which is commonly known as "cold sores" or "fever blisters." The herpes virus can be active on the skin surface without showing any signs or causing any symptoms.
Malaria was not eliminated in the United States until 1951. The term eliminated means that no new cases arise in a country for 3 years.