Stomach Flu Prevention?

It is my fiancee & my custodial time to have his 10 year old son this weekend. We just got word that he is being picked up from school for vommitting. Our thought is that we have 2 younger children in our home that we wouldn't want to expose them to it, but we don't want to lose that time with him. Is there any way to prevent the stomach flu for ourselves & our younger children? Please let me know. Thanks.