First observation

In recent days I have observed that many teenagers and children are sick now. It’s like we started new school year and after first few days lot of my friends stayed home because of a cold. I think there are few reasons of this. First - when we came back from our holidays we started to meeting so many people - crowds in school bus or in the corridor. We started exchanging bacteria. It would be very hard avoid it. So if one person was sick, by sneezing on the bus, she could infect two more etc. This situation could also be influenced by the fact that the weather was changing very quickly and unexpectedly in last two weeks. It was very hard to choose what to wear. it was easy to overheat or get cold and it could also lead to getting sick.