Can one catch the flu or infection, like herpes or cold sores, from a breathalyzer test?

They have sterile coverings, just like the thermometer at the doctor.’s office.

If the tech is an idiot probably yes, but it’s unlikely. If they remove the germy mouth piece with the same hand they put the new one, then it’s contaminated.

I once saw a nurse sneeze all over a jar of cotton swabs (no top in the jar) and then wanted to use one on me on an open wound. My sister got an eye infection after getting her eyes checked, I’m sure it’s not a coincidence. I suddenly got an infectious something on me after going to the dermatologist for a regular check up (she was going so fast she must see ten patients an hour, it was a disgrace). I had an ultrasound tech touch something in the bodily fluids trash and then put the protector on the wand for a vaginal ultrasound. I have many more examples of unclean behavior in medical facilities.

The part which touches your mouth is disposable.