(AP) — The U.S. flu season is underway. The Centers for Disease Control and Prevention on Friday released its latest flu-monitoring data, and noted sharp increases in several measures. Thirteen states last week were reporting high or very high levels of flu-like illness last week, about double from the week before. No flu strain seems to be dominant, and it’s too early in the season to know how good a match the flu vaccine will be. Flu experts suggest everyone get vaccinated, especially as people prepare to attend holiday gatherings where respiratory viruses can spread widely.