Josiah & Abi's Flight Log

So its been a while since I last posted. Its not cause nothing is going on, but rather to much is going on. Well I thought I would pose anther real life riddle. To start with I have had the chicken-pox only once in my life. I got them when I was about five years old, and was over them in a couple weeks. However five years later when I was ten, Elizabeth, Matthias, and Stephen all got the chicken-pox, and they got them from me. How can this be seeing I had the chicken-pox only once and fully recovered about five years earlier? It really happened, but how? See if you can figure it out. (For anyone out there who has already heard me tell this riddle you are not allowed to give the answer.)