swollen face then death??

Question
my daughter had 3 rats 1 male, and 2 females.. we had 2 others but they both died suddenly within and hour of each other no warning just lethargy puffed fur and then they died... we were heartbroken . Then we found 3 lovely young rats at a local petshop (they were feeders) :( .... last night my daughter cam running and was really upset about Ivey , her face was extremely swollen eyes bulging and slight rusty colored nasal discharge... she was barely breathing and died about 15 min after she found her... her cage mate rose seems fine but we have confined her to a different cage ... the male also seems fine. the only thing she did recently was change the cage bedding. she used what she had used before and the food was the same as well... we use carefresh bedding (blue) and aspen... with rat pellet food..what in the world could be causing the illnesses. she has lost 3 rats in 2 weeks and she is so heartbroken..is there any issues with allergies and bedding . i had rats growing up and used newspaper shredded up and i never had issues with them getting sick as much... they arnt in a draft area, no new foods, just the carefresh colored bedding and aspen . i am at a loss here and they died so quickly we never made it to the vet.. and they were all fine the day before ... do you have any ideas what could be happening.... my daughter takes really great care and loves them very much... thanks in advance...
Amanda

Answer
oh my that is terrible.  It is so hard to say what it could be....it may have been from a virus called SDA. Please check my site, sandyscrittercity.com and refer to the pages on health care for info on this very contagious virus. You can google it as well, looking up SDA in pet rats.

  I had a rat running around in circles screeching. He did it twice. He was fine after that but a month later he had blood all over the cage. I took him to the vet and we decided to wait and see how he was since he was acting fine. Two days later he started to behave very quiet and after I held him he went wild screeching.  We sedated him and did xrays and here he had colon cancer. I had to let him go.  I have had so many rats with odd symptoms and they pass away and usually I have a necropsy done so I can have answers.