The Sesonality of the Flu?

The number of infections went down in august, corrected. Then they came backin september with the pickinover and han. So what was the second wave due to? Why did we have that? People going back to school, for example, and whall last winter. Thit's unusual is is belief that flut propagates better in winter. And also, i think people in the school contributes to a start this thing. But also, weather seems to be important for the sesonality of lu.