Dr. Bruce Gellin: Influenza, which is a viral
infection, occurs every year. It can start as early as October and may go through May
of any given year. It tends to peak in late January, and early February. The flu tends
to circulate in the fall and winter; if you’re in the northern hemisphere, that will be between
October and February-March-April. In the southern hemisphere it’s the opposite. You really
don’t get influenza in the off-season, unless you travel to a place where influenza is circulating.