cough in the air ???

I dont know its only me, or most of us having the same issue ?

About two days ago after woke up, I felt some trouble in my throat, and here now I caught cough-so bad, so do two of nephew(toddler & baby). I though is was me, maybe of unclear air in my room ac (even its just has serviced), but unfortunately it also happen to my lovely neighbor and their children. don't know exactly where it came from (climate, poor/old ac, infected, or etc)

Just wonder