U.S. seasonal flu season is largely over, but circulates at low levels U.S. seasonal flu season is largely over, but virus continues to circulates at low levels in the United States. ATLANTA, May 4 (UPI) -- The U.S. flu season is largely over, but federal health officials say flu viruses can continue to circulate at low levels during the summer. The weekly flu report of the Centers for Disease Control and Prevention in Atlanta said for the week ending April 27 U.S. seasonal influenza activity continues to decline with all 10 regions reporting influenza-like illness activity below region-specific baselines. Baseline influenza activity is the level influenza activity remains throughout the summer and the rest of the seasons. Usually, there is a six- to 12-week period in winter when influenza activity rises above the baseline threshold -- flu season. Forty-eight states and New York City experienced minimal influenza-like illness activity. Hawaii reported low influenza-like illness activity. The geographic spread of influenza in 47 states was reported as local, sporadic, or no influenza activity. Regional influenza activity was reported in Connecticut, New Hampshire and New York. Georgia, Idaho, Kansas, Mississippi and Utah reported no influenza activity.