It is a virus.
There is no treatment for the disease - it simply runs its course.
You address the dehydration from vomiting and diarrhea by hydration therapy.
http://www.dhpe.org/infect/norwalk.html
Wash your hands...
It's a virus. The antibiotics that your friends/others are given are probably used to treat secondary infections that set in due to depleted intestinal linings and dehydration.
http://www.medicinenet.com/norovirus_infection/article.htm
It's been known as the Norwalk Virus. And, as such, it's a virus.
Regards,
Star Traveler