Why does the flu spread in the winter?

Nowadays the climate almost change rainy season will get hot ,hot season will get rain all in viceversa so , i think not in a winter season depends upon the cilmate change is the one of the most problem for flu virus ,see this winter climate wiil effect throght pain, cough , cold all deseases, next summer will come that time virul fever chance is more., rainy season also fever chance and rat fever like that will come so all time 12 months doctors have work..

I think part of it may be where we are closed in and tend to be around crowds more in the winter. Children go to school and share germs and viruses and then it spreads. The malls, etc seem to be more full in the wintertime. I tend to get the flu virus more in the springtime than during the winter. I guess it could also be the change in seasons.

I'm not quite sure, but the body is more tolerant to colds/viruses during the cold seasons because the immune system becomes weaker. Although, I'm judging this by my own immune system. I think the cold just makes it harder to do just about everything. It's harder to breathe, it's harder to exercise, it's harder to get comfortable. I'm sure it's all related some how. Again, I'm speaking about personal symptoms- other people symptoms may vary. I'd be interested to know the science behind your question, too. I hope someone will respond and enlighten us!