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Giardia is one of the most common intestinal parasites worldwide, and infects up to 20% of the world population, mostly in poorer countries with inadequate sanitation. Infections are most common in children, though chronic Giardia is more common in adults.
The Romans did not use numerals to indicate fractions but instead used words to indicate parts of a whole.
The first monoclonal antibodies were made exclusively from mouse cells. Some are now fully human, which means they are likely to be safer and may be more effective than older monoclonal antibodies.
Interferon was scarce and expensive until 1980, when the interferon gene was inserted into bacteria using recombinant DNA technology, allowing for mass cultivation and purification from bacterial cultures.
About 100 new prescription or over-the-counter drugs come into the U.S. market every year.