If a user doesn’t proactively choose to turn it on, it will be off, and snapshots will not be taken or saved.
“Yes, this is Dave from Windows Microsoft Tech Support. Yes ma’am, I’m sorry, but your computer is sending viruses to our server and this is causing a problem for us. If we do not clean the viruses from your computer, we will need to disconnect you from the internet to protect our server. But do not worry, we can fix this for you. First, I am needing you to go into settings and turn on the Windows Recall. Yes, this will help to protect your computer from the virus. Ok. Good. Hopefully this will fix the problem, but if it continues I will have to call back. Next week, I will call you back and if your computer continues to be sending these viruses, I will connect to it remotely and we will do a deeper scan for the virus. Yes, have a good day ma’am. Thank you for using Windows Microsoft.”
It’s really unlikely that alien bacteria and viruses (if alien life even uses the same building blocks ours does, such that microscopic life forms could even be called “bacteria” and “viruses”) would find our bodies terribly hospitable or be well adapted (at first) to live inside us. It’s much more likely that
Even if an alien biosphere produces some mix of oxygen / nitrogen / carbon dioxide, that the atmospheric balance will be WAY off and we won’t be able to breath it (Avatar may have gotten a bunch of science stuff wrong, but it got THIS right, unlike every other sci fi movie ever). Changing it so that we COULD breath it would probably be a major extinction level event for most life in the native biosphere.
We won’t be able to eat the local life (and it won’t be able to eat us). Our crops won’t grow in the soil (until we change it and introduce earth microbes and fungi). Once Earth life and alien life have co-existed for millions of years (long after we’re gone or evolved into something else) this may CHANGE (life forms from both biospheres may co-evolve and figure out how to parasitize and eventually consume each other).
I’m not saying we won’t die (if we ever try) for a whole host of reasons (and fuck up someone else’s environment in the process), just it won’t be (biological) alien diseases colonizing our bodies.