Can Switching from High Altitudes and dry climate and going down where is a way lower altitude and VERY humid the back up to the high Altitude and dry climate make my 4m old sick?? (<- If that made sense..)

I ask this cause we came back from visiting my Maaa in AR and he now has a super wet cough, eyes watering, and fever.

(Yes, he has a doc appointment in the morning. I was trying to lookup some different info but haven't really succeeded. Lmao)