Seasonal sickness

Sorry this is kind of a vent, but where I Iive usually when the weather starts to get cold everybody, I mean every single person is sick. I don't remember sickness being so bad when I was growing up in my native country. Is it like this where you live? How do you stay healthy?

Everytime the rain season hits, I get sick :)..... Is difficult, it's as if "sickness is in the air"

I try to stay healthy by managing stress, first and foremost. :) Then, I'll eat nutritious food and take vitamin C or D to boost my immune system. 

It's the same for me here in Nigeria,when we're approaching harmattan season,I get sick with cold and it makes me so uncomfortable,but I start to feel better after a while. I try to stay hydrated,it usually helps.