A drug-resistant stomach bug that causes diarrhea to travelers is causing outbreaks in the United States, according to the CDC. The medical name is Shigella sonnei which causes shigellosis— known as "Delhi belly" or "Montezuma's revenge." The illness is most familiar with international travelers who have experienced the stomach cramps, diarrhea, and nausea. CDC epidemiologist and local health officials tested cases in Massachusetts, California, and Pennsylvania and found that nearly 90 percent of the patients were infected were resistant to ciprofloxacin (Cipro), which usually is the first drug used to treat shigellosis. Before last year, just 2 percent of cases were Cipro-resistant.