"smth" is not an english word and I can not guess what might have been misspelled.
However, the rest of the sentence makes sense by itself.
It should be written, "A bug that's going 'round....." The last word is truly 'around', but is some times abreviated to reflect the way it is actually pronounced.
Now, for translation: A bug is a medical illness, (maybe, technically a virus). "Going around" refers to it being spread from person to person (maybe within a school, workplace, town)