Should I or should I not ?

Ok so I just got done dog sitting for my dogs and they don't take very good care of there animals and there germs got to one of my dogs and made her sick she has been sick for a week and the vet just finally figured out why she wasn't feeling good and our dog was doing so bad we thought we were going to have to put her to sleep and they ask me to dog sit again and i don't know what to do I there anyway I could keep a lot of there germs off of me o don't want my dogs to get sick again