Norwalk Viruses Widespread 
Gastrointestinal infection are often caused by the Norwalk virus or one of its many relatives. These viruses are second only to the common cold in the occurrence of viral illnesses in the US.
http://healthlink.mcw.edu/article/1031002212.htmlCDC : Noroviruses 
The organism is also known as Norwalk-like viruses or caliciviruses. The disease is also known as stomach flu or viral gastroenteritis. Includes cause, treatment, and prevention.
http://www.cdc.gov/ncidod/dvrd/revb/gastro/norovirus.htm
Norwalk Virus Gastroenteritis: A Different Type of Foodborne Illness, HYG-5569-98 
Ohio State University Extension fact sheet providing basic information on the subject.
http://ohioline.osu.edu/hyg-fact/5000/5569.html
Bad Bug Book: The Norwalk Virus Family 
Includes symptoms, sources of infection, outbreaks, and prevention.
http://vm.cfsan.fda.gov/~mow/chap34.html
eMedicine - Norwalk Virus 
Article by Michelle A Jaworski, MD.
http://www.emedicine.com/med/topic1648.htm
Norwalk Virus and Other Caliciviruses 
Scientific and medical information about the virus.
http://gsbs.utmb.edu/microbook/ch065.htm
Norwalk Virus 
Factsheet on the disease.
http://www.lambtonhealth.on.ca/communicable/norwalk.asp
BioMed Central :A summertime peak of "winter vomiting disease": Surveillance of noroviruses in England and Wales, 1995 to 2002 
Research article on the disease.
http://www.biomedcentral.com/1471-2458/3/13
Food Safety Research Information Office: Norwalk Virus 
Directory of press releases, articles, resources, and factsheets on the disease.
http://fsrio.nal.usda.gov/document_reslist.php?product_id=141