I rarely get coughs and colds, as a rule if I get sick it's big time stuff like heart trouble or diabetes etc, luckily that's a rarity but the consequences are usually permanent.

Maybe a fungal thing, all the decaying leaves and shorter damper days mean that pollen takes a back seat and spores abound. Also factor in we move from cold and damp outside to dry and warm inside. I'll hope you avoid any of that crap this year.