Cindy
My children passed step back and forth for 4 months during one summer and I finally kicked it when they went on antibiotics for 30 days at the same time. Also, I got them new toothbrush, toothpaste, washed all linens and towels immediately. They now have towels assigned to them by color, and use a dixie cup to rinse after brushing, to avoid sharing a cup. This has really helped avoid reacurrances and from passing it to each other if one came down with it later on.