Norovirus is a common cause of diarrhea. Symptoms are vomiting, abdominal cramps, and diarrhea that usually resolve in 1 to 3 days. Diagnosis is based on clinical suspicion, and polymerase chain reaction testing as part of a multiplex panel for a variety of causes of acute gastroenteritis can be done. Treatment is supportive with oral fluids; in more severe cases, IV fluids may be needed.
Since the introduction of rotavirus vaccines, norovirus has become the most common cause of acute sporadic and epidemic viral gastroenteritis in the United States in all age groups, including in children; the peak age is between 6 months and 18 months.
Infections occur year-round in the United States, but most occur from November to April (1). Large waterborne and foodborne outbreaks occur.
Person-to-person transmission also occurs because the virus is highly contagious. Norovirus causes most cases of gastroenteritis epidemics on cruise ships and in nursing homes.
Incubation period is 24 to 48 hours.
(See also Overview of Gastroenteritis.)
Reference
1. Centers for Disease Control and Prevention (CDC): Norovirus Burden and Trends. Accessed May 12, 2023.
Symptoms and Signs of Norovirus Gastroenteritis
Norovirus typically causes acute onset of vomiting, abdominal cramps, and diarrhea, with symptoms usually lasting 1 to 3 days. In children, vomiting is more prominent than diarrhea, whereas in adults, diarrhea usually predominates.
Fluid losses vary from mild to severe dehydration.
Patients may also have fever, headache, and myalgias.
Pearls & Pitfalls
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Diagnosis of Norovirus Gastroenteritis
Sometimes reverse transcriptase–polymerase chain reaction (RT-PCR) testing
Diagnosis of norovirus is usually based on clinical suspicion in a patient with typical symptoms, especially during an outbreak.
Laboratory testing can confirm the diagnosis of norovirus infection using RT-PCR on a stool sample. This test is usually done as a multiplex PCR panel including a number of causes of gastroenteritis. Caution must be used when interpreting a positive test result for norovirus because there can be asymptomatic shedding, which the very sensitive PCR test can detect. A positive test result for norovirus in a patient with atypical symptoms, such as bloody diarrhea, or in a patient testing positive for another pathogen suggests that norovirus is not the cause of the gastroenteritis.
Treatment of Norovirus Gastroenteritis
Oral or IV fluids
Sometimes antidiarrheal agents and/or antiemetics
Supportive care, including rehydration with fluids and electrolytes, is the mainstay of treatment and is all that is needed for most adults. Oral glucose-electrolyte solutions, broth, or bouillon may prevent dehydration or treat mild dehydration. Children may become dehydrated more quickly and should be given an appropriate oral rehydration solution (several are available commercially—see Oral Rehydration
Isotonic IV fluids such as Ringer’s lactate and normal saline solution should be given when there is severe dehydration, hypovolemic shock, or altered mental status and ileus or failure of oral rehydration therapy (see also the Infectious Diseases Society of America's [IDSA] 2017 clinical practice guidelines for the diagnosis and management of infectious diarrhea). In severe dehydration, IV rehydration should be continued until pulse, perfusion, and mental status normalize.
Antidiarrheal agents should not be given to children < 18 years of age with acute diarrhea (see the IDSA guidelines). Antidiarrheals can be considered in adult patients with watery diarrhea (as shown by heme-negative stool), especially during an outbreak, suggesting a viral cause is likely. However, antidiarrheals may cause deterioration of patients with Clostridioides difficile or E. coli O157:H7 infection and thus should not be given to any patients in whom the cause of diarrhea has not been identified and in whom these disorders may be suspected (ie, based on recent antibiotic use, bloody diarrhea, heme-positive stool, or diarrhea with fever).
Key Points
Norovirus is the most common cause of acute viral gastroenteritis in the United States in all age groups.
Clinical course is short but can involve severe vomiting and diarrhea.
Oral rehydration is usually adequate, but antiemetics and sometimes IV fluids may be needed.
Antidiarrheal agents are safe for adults with watery diarrhea but should be avoided in children < 18 years of age and in any patient with recent antibiotic use, bloody diarrhea, heme-positive stool, or diarrhea with fever.
More Information
The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
Infectious Diseases Society of America: Clinical practice guidelines for the diagnosis and management of infectious diarrhea (2017)
