(Undated) — The flu is spreading in parts of the U.S. but not yet in the Midwest. Southern and Southeastern states have high to very high numbers of confirmed influenza cases, according to the Centers for Disease Control. Most Midwest states, including Iowa have a minimal number of cases, so far. The flu season generally starts in October and November and runs through May. The season usually peaks in February. The CDC says the flu vaccine appears to be a good match for the strains of flu being seen this fall.