Norovirus or Norwalk Virus

What is the Norovirus or Norwalk Virus?

It is estimated that nearly 65% of nonbacterial gastroenteritis in the US is attributable to Norwalk and Norwalk-like viruses. 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 and Norwalk-like viruses also are referred to as "noroviruses." infection symptoms include nausea, vomiting, diarrhea and abdominal cramps. The incubation period is between 12 and 48 hours (average of 36 hours, with usual duration of 12-60 hours. 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. Although food is an efficient means of transmitting these agents, Norwalk and Norwalk-like viruses can be transmitted via water and by person-to-person contact. 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.

More Information on Norovirus:

• Centers for Disease Control and Prevention
• Norwalk virus - Foodborne Pathogenic Microorganisms and Natural Toxins (Bad Bug Book)
• Norwalk-like Viruses. Morbidity Mortality Weekly Reports