FIRST DESCRIBED IN 1929 as “winter vomiting disease,” norovirus infection is caused by a group of viruses that are the most common cause of gastroenteritis: They're responsible for over 23 million cases annually.1,2 Because they were first identified in a gastroenteritis outbreak in Norwalk, Ohio, they were previously called Norwalk-like viruses.3 One in 14 Americans become ill from norovirus infections each year, resulting in 91,000 ED visits and 71,000 hospitalizations.4 All age groups are susceptible, but older adults may have more severe outcomes and longer illness.4
Hospitalized patients who are immunocompromised or who have significant medical problems can have a longer length of stay and additional medical complications. They're also at greater risk for relapse. Some patients with norovirus infection die, although this is rare.
Noroviruses are classified into six subgroups, with multiple variants emerging and becoming the predominant causes of disease.5 Reasons include increased pathogenicity and transmissibility, and decreased population immunity.2
How noroviruses are transmitted
Introduced into healthcare facilities by patients, visitors, or staff, noroviruses may be responsible for more than 50% of hospital and long-term-care gastroenteritis outbreaks.2 Outbreaks have also been reported in schools, day-care centers, hotels, prisons, restaurants, and cruise ships. Norovirus can contaminate curtains, carpets, cushions, bedside commodes, toilets, handrails, faucets, telephones, door handles, kitchen surfaces, and elevator buttons. Norovirus is very stable in the environment and can persist for up to 28 days.2
Noroviruses are highly contagious. They're easily transmitted from contaminated foods such as bakery products, shellfish, sauces, sandwiches, fruits, vegetables, and salads; the hands of ill food handlers who prepare meals (fecal-oral transmission); and water (from wells, ice, lakes, swimming pools).1 Aerosol exposure from vomiting persons can lead to norovirus being swallowed.
In healthcare settings, transmission is most likely via direct contact with infected persons or contaminated equipment. The virus can be transferred from hand to mouth after someone touches contaminated items. Close proximity to patients with norovirus infection increases the transmission risk.
Norovirus infection has a 12- to 48-hour incubation period. Patients may develop nausea, acute-onset vomiting, cramping, malaise, watery nonbloody diarrhea, abdominal cramps, myalgia, headache, or low-grade fever for 2 to 5 days. However, approximately 30% of infections are asymptomatic.6
No specific therapy is available to treat norovirus. The infection is self-limiting and most patients make a full recovery without treatment in 48 to 72 hours.3 Dehydration is the most common complication due to vomiting and diarrhea. Treatment involves replacing fluids and correcting electrolyte imbalances. Oral and I.V. fluid replacement may be prescribed.
Norovirus immunity to the strain that caused the infection can last several weeks after the illness, but no long-term immunity or vaccine exists to prevent reoccurrences.
Determining norovirus infection
The gold standard for diagnosing norovirus infection is the reverse transcriptase-polymerase chain reaction assay performed on stool specimens. Several specimens may be needed to confirm the diagnosis. Obtain specimens within 2 to 3 days of symptom onset. Vomitus may be used when fecal specimens aren't available but is less likely to be positive because viral concentrations are lower. Detecting norovirus in food samples is technically difficult and expensive, so food testing isn't routinely performed.1
Patients with norovirus infection should be placed in a single-occupancy room if possible. Use contact precautions with personal protective equipment (PPE) upon entering the patient's room.2 Practice standard precautions when exposed to vomitus or diarrhea. Wear a surgical or procedure mask and eye protection or a full face shield if you anticipate a risk of facial splashing due to vomiting or if you're cleaning surfaces visibly contaminated with vomit or feces. Viral shedding from an infected person can persist for up to 22 days following infection.2
Perform hand hygiene after removing personal PPE. The CDC recommends using ethanol-based hand sanitizers instead of isopropyl-based hand sanitizers or nonalcohol-based hand sanitizers during norovirus outbreaks.2 The Environmental Protective Agency (EPA) provides a list of registered products that are effective against norovirus at www.epa.gov/oppad001/list_g_norovirus.pdf. Wait a minimum of 48 hours after symptom resolution before discontinuing contact precautions.2
General unit cleaning and disinfection should be increased to twice a day. Frequently touched surfaces should be cleaned and disinfected three times daily using an EPA-registered product with healthcare label claims.2 Promptly clean and disinfect surfaces with visible emesis or fecal soiling.
When norovirus spreads
A norovirus outbreak is defined as two or more suspected or confirmed cases among staff or patients. Managing an outbreak is challenging.4 Implement multiple interventions to bring the outbreak under control. Exclude nonessential staff from working in areas that are experiencing an outbreak. Visitor privileges may need to be suspended. Norovirus outbreaks may lead to room closures for new admissions/transfers and additional expenditures with isolation precautions/PPE, additional environmental cleaning, staff cohorting/replacements, and employee sick time. Ill patients may be cohorted in a multioccupancy room.
The CDC has additional recommendations when encountering a norovirus outbreak; visit www.cdc.gov/hicpac/pdf/norovirus/Norovirus-Guideline-2011.pdf for a complete list.