Norwalk virus typically incubates in humans for 24-48 hours. However it is possible to be infected after only 12 hours after exposure. Although people are not typically long term hosts of the virus, current research is examining for how long hosts continue to shed after the cessation of symptoms. New research suggests that humans may shed infectable virus for up to three weeks after the cessation of symptoms.
Globally, there are almost 23 million cases of Norwalk virus that occur each year. Norwalk virus and Norwalk-like virus infections account for almost half of the outbreaks of foodborne gastroenteritis. Norwalk infections usually occur in clusters, also known as outbreaks, and typically affect schools, camps, cruiseships and hospitals.
Norwalk virus typically presents as vomiting, followed by extensive diarrhea. The vomiting and diarrhea is sometimes accompanied by stomach cramps, nausea, and low-grade fever. Small children and the elderly are more likely to become dehydrated.
The outcome is invariably good with very rare occurrence of death in healthy people, and people are unlikely to experience any last side effects from the infection.
Currently there is no real treatment for Norwalk virus gastroenteritis. Management consists of trying to maintain body fluids (because of the tendency to become dehydrated from the diarrhea), as well as maintain proper electrolyte balance. Patients can use either oral rehydration therapies or intravenous therapies.
The prevention of Norwalk virus consists of proper hygiene as well as ensuring that water and food sources are not contaminated. Proper and frequent handwashing (especially for workers in the food preparation industry) is crucial to eliminating Norwalk outbreaks. Additionally, it is important for research to continue in better ways to test water for Norwalk viruses, because the Norwalk virus is fairly hardy and can survive in the levels of chlorine in public drinking water.