The concept of measuring "viral copies" in breath is pretty cool, seems like a brand new technique? I can see it being invaluable in studying respitory viruses

The concept of measuring "viral copies" in breath is pretty cool, seems like a brand new technique? I can see it being invaluable in studying respitory viruses going forward. The only shortcoming of this study is the lack of data points _prior_ to symptoms. One of the hotly contested points of hygiene policy during the pandemic was about how the virus spreads before symptoms show up. I'm unsure if there's a study that already settles this, but this new method seems like a sure fire way.