Mouse's miraculous recovery

I'm down to one mouse the others went very suddenly, a few weeks apart, losing weight rapidly and slowing down and I assumed a natural death of old age... the last one died last week. My remaining mouse, Dita started going the same way - on clean out day we found her in her bed frozen and skinny - even though all the food in the cage was gone and I assumed we would be losing her too - she wouldn't even take nutrical which her sisters gobbled up even on their last legs. Because she was so cold I moved her into the bathroom where it's warm and steamy so she's be comfortable at least. This was a week ago and since then she's put on weight and is zooming about the cage like a baby She is doing a funny head-shaking thing, like bruxing but much more exaggerated... any body have any ideas what might have happened here? The only thing I can think is resp infection helped by the steam in the bathroom maybe?

Pneumonia I would guess... blimey, not very old were they? only a year ish? I thought you got them at the last Bradford?

Poor little mites.

xx

Yeah last Jan. Though 2 of them were babies but the other 2 were adults and I don't know how old they were at the time. She's still with us as of this evening anyway