Composed of a single cell, amoeba seem harmless enough: They look like playful critters waltzing under the spotlight of a microscope until they come upon a group of bacteria. Then, these previously ...

The single-celled parasite Entamoeba histolytica infects 50 million people each year, killing nearly 70,000. Usually, this wily, shape-shifting amoeba causes nothing worse than diarrhea. But sometimes ...