Originally Posted by
Icelanta
Since when does a small dog or cat in a bag/petcase transmit any disease?! 🙄
Mostly: when they come out of the bag/petcase, which they will do at some time. This is why carrying your pet in a bag/petcase does not exempt you from pet quarantine requirements, where they exist. This applies even if you use your own entire aircraft as the bag/petcase (see e.g. Jonny Depp).
However, when talking about respiratory viruses and aerosol transmission the answer is "when the bag/petcase exchanges air with the outside". So, yeah you're right, no problem,
as long as the bag/petcase is certified escape-proof and airtight...