Sounds like the flu (virus). They've finally found a name for it!
Flu has a name for the virus: Influenza. Tends to be more respiratory problems. RNA based, but I forget if it's single or double stranded.
http://www.cdc.gov/flu/about/fluviruses.htmNorwalk is something totally different, often strikes in winter. Single stranded RNA virus. Tends to have more GI symptoms.
http://www.cdc.gov/ncidod/dvrd/revb/gastro/norovirus.htm