Lice came out of nowhere

We moved in these apartments almost 3 months ago and about a week ago my son.has been scratching his head.and.a little after I became somewhat itchy too and this morning I looked through his hair.and I saw.2 lice eggs!!! We have not slept over anyones house nor has anyone slept over or even came.over so I have no.idea where they came from??? Has this happened to anyone else?