Symptoms
Infection with norovirus manifests as gastroenteritis with diarrhea without blood in the stool and/or with violent, even explosive vomiting. Vomiting is more common in children. Furthermore, accompanying symptoms such as nausea, bloating, abdominal pain, abdominal cramps, muscle pain, headache, and mild fever may occur. An asymptomatic course is also possible. The duration of the illness is 1 to 3 days or short, but may be prolonged, for example, in the elderly. The diarrhea with vomiting often lasts only a few hours. Norovirus infections are more common during the cold season. Because of its rapid spread, larger local outbreaks occur wherever people live together in close quarters. For example, in nursing homes, hospitals, cruise ships, hotels and camps, the military, tent camps, schools, and daycare centers. The disease is usually benign. However, it can lead to dangerous dehydration, complications such as hypokalemia, cardiac arrhythmias, graft rejection, kidney failure, and death, especially in the elderly, infants, young children, and people with underlying diseases.
Cause
The cause of gastroenteritis is norovirus, a genetically diverse, nonenveloped, single-stranded RNA virus of the calicivirus family. The viruses replicate in the small intestine and are shed in stool and vomit. They cause delayed gastric emptying and motility, resulting in nausea and vomiting. Noroviruses can survive on surfaces for perhaps up to a month and are relatively temperature resistant (-20°C to +60°C). Brief boiling inactivates them. In addition, very few viruses (10 to 100, up to 1000) are sufficient for infection. Immunity is short, and repeated infections with the same or other strains are possible.
Transmission
For successful infection, viruses must enter the intestine perorally. They are passed directly from person to person through feces (fecal-oral) or vomit. Because they remain contagious for a long time outside the host, they are spread through contaminated objects (e.g., doorknobs, computer keyboards, toilets), water, and food (e.g., fruits, lettuce, pastries, oysters, and other shellfish). The incubation period is 10 to 50 hours. Infected individuals are contagious just before the onset of symptoms, during illness, and days (perhaps even weeks) after illness. Numerous case studies have been described in the literature, illustrating the high risk of infection and the need for good hygiene measures. For example, a sick baker in the Netherlands infected 231 people who ate from his rolls, which in turn led to numerous outbreaks in the Netherlands and England (de Wit et al., 2007). A single concertgoer from Wales who vomited in the auditorium and toilet during a concert infected more than 300 people in total (Evans et al., 2002).
Diagnosis
Suspicion is already possible based on clinical symptoms and transmission (diarrhea, vomiting, high rate of infection, short duration), but acute diarrheal illness can also be caused by other pathogens and causes (e.g., rotavirus, longer duration). Laboratory methods are available to confirm the diagnosis, especially highly specific and sensitive reverse transcriptase polymerase chain reaction (RT-PCR).
Prevention
For prevention, hygiene measures are key. Preventing transmission during a local outbreak requires great effort. In the event of an outbreak in a class camp, a home, or a hotel, for example, special measures must be taken. The Federal Office of Public Health FOPH provides extensive information on this topic on its website.
Nonpharmacologic treatment
The disease is usually self-limiting and does not necessarily require drug therapy. The emphasis is on fluid and electrolyte replacement and appropriate symptomatic therapy, especially in those at risk (infants, young children, the elderly, people with chronic diseases). If the condition of the permits, bouillon, broth, tea, sweet drinks and light food can be administered.
Drug treatment
Not all of the medications listed are appropriate for children and special patient populations (see the Specialty Information). As mentioned earlier, medications are not necessary in every case.Oral rehydration solution:
- Oral rehydration solution contains glucose, salts, and water and is used to replace lost fluids and electrolytes. Infusions may be administered if the course is severe.
Anti-nausea agent:
- Prokinetic agents such as the dopamine antagonists domperidone or metoclopramide are used to treat nausea and vomiting. They inhibit nausea and promote gastric emptying and decreased motility, which trigger these symptoms. Antihistamines such as meclozine do not promote motility but may also be effective against nausea.
Anti-diarrheal agents:
- A number of drugs are available for the treatment of diarrhea. Among the most effective is loperamide. Alternatively, herbal remedies such as black tea or probiotics can be used. Charcoal is an old home remedy; its effectiveness is controversial among experts.
Antispasmodics:
- For example, scopolamine butyl bromide can be used to treat abdominal cramps. Peppermint oil or chamomile are two possible herbal alternatives. A hot water bottle often helps with the acute symptoms.
Painkillers:
- Such as acetaminophen or ibuprofen can be taken as needed for fever, pain and headache or administered as suppositories. NSAIDs can further irritate the mucous membranes.
Antivirals:
- Are not yet available. Treatment so far is based on symptoms. Antibiotics are not indicated because it is not a bacterial infection.
Vitamins and minerals for the recovery phase.
