Approximately 181,000 cases occur annually, with no known associated deaths. Norwalk and Norwalk-like viruses have been associated with outbreaks on cruise ships and in communities, camps, schools, institutions and families. Foods such as raw oysters, cake frosting and salads, as well as drinking water, have been implicated as a common source of viral infection in several outbreaks. Norwalk virus infection symptoms include nausea, vomiting, diarrhea and abdominal cramps. Symptoms experienced less often include headache, fever, chills and myalgias.
Fluid replacement is the common therapy.
Transmission of Norwalk virus is through the fecal-oral cycle. Transmission is of special concern for the fishing industry, since molluscan shellfish, being filter feeders, are readily contaminated with the stool-shed viruses present in human sewage. This page was updated on March 30, 2000.