Mice suddenly biting

Question
Hello again. I have asked you before about my two mice, Squeek and Ryoko. Well, they have been doing fine, and not getting baths. :) But recently both of them have started to bite both me and my fiance when when pick them up. It started with small nibbles, nothing painful. As suggested I tapped them on their nose and they stopped biting while we held them. But in the past two days both Squeek and Ryoko have bit me hard. Thankfully Squeek went after my finger nail, but Ryoko broke my skin. No blood though.
What in the world could be causing this sudden change in behavior?

As a side note- I recently found a little brown mouse running around in my apartment. I caught it and released it at my friends farm. But is it possible it transmitted something to my mice to make them aggressive? Herman, as I named it, was never in their cage with them. I was to paranoid about that. (it was female by the way, I don't know why I called it Herman)

Thank you

Answer
Dear Danielle,

I took an extra day to answer because I wanted to consult with other mouse experts. None of us had the best answers for you, but here are some ideas.  The problem is- why would two mice simultaneously have a character change?

If the mice did get something from the wild mouse, through contact with your hands or clothing or through a very small air space, it is possible that they might not be feeling well.  This might cause them to nip.

By the same token they might have gotten some other disease some other way, at the same time, or be sick from food or chemicals, which would upset them both.

If you had something that smelled edible on your hands at the time you held them, that would of course be an obvious solution.

If something happened to traumatize them or even upset them, they might be prone to bite.  This could be temporary or long-lasting. This might have something to do with you personally or with an event when you weren't around.

If this continues and they do try to break the skin, you'll need to wear gloves to handle them.  I hope it doesn't get that bad.

Best of luck.  

squeaks,

Natasha

PS That's funny about Herman.  Perhaps you meant Hermione? However, historically girls do get named male names and eventually the men don't want to use those names anymore, such as the name Leslie.  Never again will a boy wild mouse in your neighborhood want to be known as Herman!