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Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.
The longest a person has survived after a heart transplant is 24 years.
Cancer has been around as long as humankind, but only in the second half of the twentieth century did the number of cancer cases explode.
A cataract is a clouding of the eyes' natural lens. As we age, some clouding of the lens may occur. The first sign of a cataract is usually blurry vision. Although glasses and other visual aids may at first help a person with cataracts, surgery may become inevitable. Cataract surgery is very successful in restoring vision, and it is the most frequently performed surgery in the United States.
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.