Snapshot A 25-year-old man presents to his primary care physician for vomiting and diarrhea. He reports that he recently went on a 3-day cruise to the Caribbean. Two days after returning home, he started feeling nauseous and has had 3 episodes of nonbloody, nonbilious vomiting and watery diarrhea. He has been trying to drink fluids but has not been successful due to nausea. On physical exam, his mucous membranes are dry and his abdomen is soft and nontender to palpation. He is given a liter of normal saline and stool studies are sent. Introduction Classification norovirus a non-enveloped, linear, single-stranded, positive-sense RNA virus with an icosahedral capsid a calicivirus formerly known as “Norwalk” virus causes gastroenteritis transmission via direct contact or fecal-oral Epidemiology incidence most common cause of nonbacterial gastroenteritis more common in winter demographics all ages risk factors close living quarters dorms military ships cruise ships Pathogenesis the virus is highly contagious the virus causes damage to small intestine microvilli enzymatic dysfunction at the brush border causes diarrhea the virus also causes delayed gastric emptying and motility dysfunction, resulting in vomiting Prognosis symptoms occur 1-2 days after exposure to virus typically self-limited Presentation Symptoms nausea vomiting watery diarrhea headaches myalgia Physical exam abdominal exam may have diffuse tenderness or none Studies Labs detection of serum antibodies (IgM) to norovirus stool studies no fecal leukocytes no occult blood stool culture to exclude other agents Making the diagnosis most cases are clinically diagnosed Differential Salmonella gastroenteritis distinguishing factor typically has fecal leukocytes and occult blood on stool studies Treatment Management approach the mainstay of treatment is supportive care Conservative supportive care indication all patients modalities intravenous hydration electrolyte repletion anti-emetics analgesics Complications Dehydration