Influenza has officially reached epidemic proportions in the United States, with 7.3 percent of deaths last week caused by pneumonia and the flu, the U.S. Centers for Disease Control and Prevention said on Friday. That is just above the epidemic threshold of 7.2 percent. Nine of the 10 U.S. regions had "elevated" flu activity, confirming that seasonal flu has spread across the country and reached high levels several weeks before the usual time of late January or February. The other region, the Southwest and California, had "normal" flu activity last week.