Hi,
When I clicked on the popup showing that Avast updated itself, I was surprised to find in the Virus update History many updates for Android. So, why does avast on a PC update virus definitions for Android?
Why not, people connect to their PCs with their android phones.
If you search all of the signature updates (a monstrous task) you will probably find linux and Mac related signatures, they are there for the same reasons.
Thank you. Didn’t think of that 
You’re welcome.