NEW YORK -- A new strain of stomach bug sweeping the globe is taking over in the U.S., health officials say.Since September, more than 140 outbreaks in the U.S. have been caused by the new Sydney strain of norovirus. It may not be unusually dangerous; some scientists don't think it is. But it is different, and many people might not be able to fight off its gut-wrenching effects.Clearly, it's having an impact. The new strain is making people sick in Japan, Western Europe and other parts of the world. It was first identified last year in Australia and called the Sydney strain.In the U.S., it is accounting for about 60 percent of norovirus outbreaks, according to report released Thursday by the Centers for Disease Control and Prevention.Norovirus -- once known as Norwalk virus -- is highly contagious and often spreads in places like schools, cruise ships and nursing homes, especially during the winter. Last month, 220 people on the Queen Mary II were stricken during a Caribbean cruise.Sometimes mistakenly called stomach flu, the virus causes bouts of vomiting and diarrhea for a few days.Every two or three years, a new strain evolves -- the last was in 2009. The Sydney strain's appearance has coincided with a spike in influenza, perhaps contributing to the perception that this is a particularly bad flu season in the U.S.