Norwalk Virus Profile

Incubation
The incubation for Norwalk virus is usually between twenty-four to forty-eight hours after initial infection.  However, symptoms can appear as early as twelve hours after exposure to the virus.

Epidemiology
It is estimated that 23 million cases of acute gastroenteritis worldwide are due to norovirus infection.  Furthermore, it is though that at least half of all food related outbreaks of gastroenteritis are due to noroviruses.  Norwalk virus is the leading cause of viral gastroenteritis in the United States, accounting for approximately 40% of nonbacterial gastroenteritis cases.  The virus is highly infectious and it’s transmitted through the fecal-oral route.  Cases of norovirus tend to occur in clusters and are commonly found in schools, camps, nursing homes, and cruises.

Symtomatology/outcomes
Infection with Norwalk virus is characterized by acute-onset vomiting, diarrhea, abdominal cramps, and nausea and is occasionally accompanied by a low-grade fever.  The most common complication is dehydration, especially among the young and the old.  The symptoms tend to last for 1-2 days and recovery is usually complete.  Immunity is established after infection; however, this immunity appears to only last for several years.   

Management/prevention
Specific therapies or treatments for norovirus do not exist.  However, treatment of dehydration is of utmost importance and can be done through oral rehydration therapy or intravenously.  Additionally, it is important to replace lost electrolytes which can also be done through intravenous.  Norovirus transmission through food can be limited by correct and thorough hand-washing.  Additionally, people in the food industry should take care not to work on when they are suffering from gastroenteritis. 

References
CDC: http://www.cdc.gov/ncidod/dvrd/revb/gastro/norovirus-factsheet.htm

eMedicine: http://www.emedicine.com/med/topic1648.htm

Strauss, James H. & Strauss, Ellen G. Viruses and Human Disease.  San Diego: Academic Press, 2002.