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There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
The U.S. Preventive Services Task Force recommends that all women age 65 years of age or older should be screened with bone densitometry.
Vaccines prevent between 2.5 and 4 million deaths every year.
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.
After 5 years of being diagnosed with rheumatoid arthritis, one every three patients will no longer be able to work.
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