system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What causes flu season? Where does it go during the summer months and how does it come back?
gpt
It is not so much that it is a "season, but rather the conditions that occur. The easiest way to spread the flu is to be is close contact with people. During the colder winter months, people stay inside more often and that causes exposure to more people that might have the flu. Compared to summer where people are outside more often and although they may come into contact with someone who has the flu, they are not constantly exposed to multiple people who have it.