wild house mouse house guest

Question
Right after the ball dropped this New Year my cat (one of three) came running through my living room hot on the tail of a small mouse. We caught the mouse in bucket before the other cats could figure out what happened. He continues to be our house guest since I live in the North East US and it is very cold. All reports suggest no warm up in sight.  I was hoping you could advise me on when it would be safe i/e warm enough to release the little guy. I figured near 40 degrees but I couldn't bear the thought of him freezing. Also how safe is it to handle a wild mouse for cage cleaning and so forth. I have had pet rats in the past but they were very tame and had no issues with standing up to my cats. I am also worried about any disease he might carry.
Thank you,  

Answer
Dear H,

Thank you for caring about the little mouse. You started your New Year with good karma, though the little mouse didn't get the best start.

A house mouse isn't used to the cold, so if it's possible I suggest keeping it until it's about 50 degrees at night.  Then you need to take it well over a mile from your house to let it go; otherwise you may be seeing it again.  Find a place with lots of cover, like a forest or meadow, and leave a pile of mouse food for it.  

While you have the mouse in a cage, you probably won't be able to handle it without gloves on.  When you clean the cage, just don't stick your face in the dirty bedding, because the one disease people occasionally get from wild mice, the hantavirus, comes from breathing in ancient mouse pee such as when cleaning an old barn or attic.  This virus is incredibly rare and basically does not exist in the Northeast, so I would not worry at all if I were you.  

You may find you can't handle it at all.  In this case you may find it is easiest to clean the cage in parts.  While the mouse hides in one half, you switch out the bedding in the other half.  I recommend doing this in the bathtub, so if the mouse does get loose it can't escape into the house.  

It is crucial that there be a wheel in the cage.

Have fun with your little unexpected house guest.

Squeaks n giggles,

Natasha