Clinical Presentation: Norovirus infections are characterized by the abrupt onset of nonspecific gastrointestinal and constitutional symptoms, which usually include nausea, vomiting, diarrhea, and some stomach cramping. Additionally, some persons have low-grade fever, chills, headache, muscle aches, and malaise. In most people the illness is self-limiting with symptoms lasting for about 1 or 2 days. Dehydration is the most common complication and may require intravenous replacement fluids.

Transmission: Norovirus is very highly contagious and is transmitted in stool and vomitus. Exposure can result through direct contact with a person who is ill, by consuming food or liquids that are prepared or handled by an ill person, and through contact with surfaces or objects contaminated by vomitus or stool. The virus can persist on surfaces for prolonged periods at a wide range of temperatures. Noroviruses can also spread via a droplet route from vomitus.

Diagnosis: In outbreaks and clusters of illness, particularly in institutional settings, it is recommended that a diagnosis be confirmed through laboratory viral RNA by reverse transcriptase polymerase chain reaction (RT-PCR) testing of stool specimens at the Maine CDC's Health and Environmental Testing Laboratory (HETL). In any outbreak of diarrheal illness, stools should also be tested for bacterial and parasitic pathogens through the routine testing processes available in that setting.

Clinical Management: No specific therapy exists for norovirus gastroenteritis. Symptomatic therapy consists of replacing fluid losses and correcting electrolyte disturbances through oral and intravenous fluid administration.

Prevention: In the community, persons with acute gastroenteritis should be told that infection can be easily spread from person to person, and that both stool and vomit are infectious. Particular care should be taken by ill persons who prepare food for others, and with young children in diapers who may have diarrhea. Patients and their close contacts should wash their hands frequently with soap and water, and should be aware that contagion will likely continue for at least 3 days after recovery from their symptoms.