Norovirus: duration, course, treatment, incubation period

Norovirus: duration, course, treatment, incubation period

A norovirus infection is an acute gastrointestinal disease with severe vomiting and diarrhoea. It is triggered by the Norovirus. Infection is easily transmitted through contact with the sick, contaminated objects or (raw) food. Usually the infection lasts only a few days and subsides without permanent damage. For small children and older people, however, the high fluid loss of Norovirus can be dangerous. Read all important information about Norovirus!

, Norovirus: duration, course, treatment, incubation period

Short overview: Norovirus

  • Description: A very contagious gastrointestinal disease caused by noroviruses.
  • High risk of infection: Norovirus is transmitted directly from person to person, via contaminated objects or food, and via droplet infection.
  • Symptoms: Nausea, gushing vomiting, diarrhoea, headache, abdominal pain and aching limbs, slight fever, fatigue
  • Treatment: symptomatic therapy by compensating for the loss of fluid and electrolytes; possibly remedies against vomiting (antiemetic); in-patient therapy in hospital and infusion in severe cases
  • Prognosis: Norovirus usually heals without any problems in otherwise healthy adults. Small children and the elderly are more susceptible to complications due to the heavy loss of fluids and electrolytes.
  • Obligation to report: Proven infections must be reported. In humans working with food or in public places, the suspicion of norovirus must also be reported.

What is Norovirus?

The Norovirus is a worldwide spread virus type. It is very resistant to adverse environmental influences: The pathogen survives on food (even refrigerated) as well as on surfaces such as door handles, taps, stair railings or toilet seats. It can even survive temperatures of up to 60 degrees for several minutes.

Noroviruses are not more dangerous than other diarrhoea pathogens, but they are significantly more infectious than many other germs. A minimum number of viruses is sufficient for an infection. By the way, they can also be transmitted via vomit, which typically occurs at the beginning of a norovirus disease.

It is important that you disinfect your hands after using the toilet – with a norovirus-suitable agent. You must also treat all surfaces that are touched, such as the rinse and tap. And: Do not use cutlery or glasses together. After an infection, there is no immunity, so you can get infected with noroviruses again and again.

The best protection against infection with noroviruses is good hygiene with thorough washing of hands. So, soap and rinse for at least 30 seconds – and not only after going to the toilet, but also before making dinner. When using public toilets, the use of a hand disinfectant solution – which is available in small bottles to take away – can provide additional protection.

Attention: Many disinfectants are not sufficiently effective against noroviruses. Only preparations with proven effectiveness against viruses (virucidal effectiveness) are suitable.

According to the Robert Koch Institute, noroviruses are responsible for the majority of non-bacterial gastrointestinal inflammations (medical gastroenteritis). In children they cause about 30 percent of all gastroenteritis diseases and in adults up to 50 percent.

In principle, there is a risk of infection with Norovirus all year round. The duration and course of the infection depends on the general state of health of the patient. There is no evidence of residual damage after infection with Norovirus.

Norovirus: routes of infection and protection

Noroviruses are very contagious. Even the smallest amounts of ten to 100 virus particles are enough for a human being to become ill with the norovirus. Even a single infected person can be enough to cause a local epidemic!

The norovirus can be transmitted directly from person to person: The vomit and stool of a sick person contains many viruses. Tiny remnants of the excretions containing noroviruses can be transferred to other people via the hands, for example when shaking hands. If the healthy person then unconsciously grabs his mouth or nose with the hand in question, the viruses can easily enter his body via the mucous membranes. This is called the fecal-oral route of infection.

A so-called smear infection via contaminated objects such as door handles or cutlery is also possible with Norovirus infections. Even on food and in liquids the viruses can survive for some time. For example, there have been some local Norovirus epidemics in the past, triggered by contaminated food or drinks (salads, mussels, water, etc.).

In addition, one can also become infected with Norovirus when fine droplets are formed during vomiting and enter another person’s mouth or nose through the air. This is called droplet infection.

Note: According to current knowledge, the norovirus is only transmitted between humans, but not between humans and animals.

Norovirus: How long have you been contagious?

There is a risk of infection immediately after infection with noroviruses (see below: incubation period). It is particularly large as soon as symptoms appear. However, patients are still contagious up to 48 hours after the symptoms have subsided. The viruses can even be detected in stool for up to 14 days, in individual cases even longer. Throughout this time you should therefore pay attention to careful hygiene.

Norovirus: Very often in winter and in communal facilities

During the cold season the immune system is often slightly weakened. The mucous membranes are then also less protected against pathogens. This is why norovirus outbreaks are particularly frequent during the winter months. However, cases of illness are also possible during the rest of the year.

The viruses spread particularly quickly in places where many people are together in a manageable space. For example, hospitals, community facilities such as retirement homes or nursing homes, and schools can become veritable “Norovirus incubators”. Such outbreaks are usually due to insufficient hygiene measures.

Norovirus: How to protect yourself

You cannot specifically prevent an infection with the Norovirus: There is no Norovirus vaccination available yet. However, you can reduce the risk of being infected with Norovirus by taking the following measures:

  • Meticulous hygiene. Above all, you should wash your hands regularly and thoroughly, especially before eating and after going to the toilet.
  • Disinfect. You can also use a Norovirus-effective disinfectant, which is available in the pharmacy, to wash your hands. The disinfectant must act for 30 seconds to prevent norovirus transmission. Also all objects that a sick person touches in the household should be disinfected if possible. These include, for example, door handles, light switches and cutlery. It is best to wear gloves, as surface disinfectants are usually harmful to the skin. A mouthguard is also recommended to avoid inhaling virus particles.
  • Washing. Make sure that laundry that the person concerned has used is always washed immediately. Select a washing temperature of 90 degrees Celsius to kill any noroviruses that may be present on it.
  • Avoid contact. Affected persons should stay at home for up to two days after the infection to avoid infecting other people.

Note: Hygiene measures should be maintained for at least one week after the symptoms have subsided. This is especially true for the conscientious washing and disinfecting of hands.

Many sufferers believe that they are immune after an infection with the norovirus and thus protected from further diseases. But this only applies to the exact same virus. However, noroviruses have a large number of different subtypes that are constantly changing. Therefore there is no immunity against Norovirus after surviving infection. The high number of subtypes is also the reason why the pharmaceutical industry is not involved in the development of a vaccine: It is almost impossible to cover all subtypes by vaccination.

Attention: After surviving the disease you are not immune to Norovirus! The viruses are too mutable for this. An infection with the norovirus can therefore occur again at any time, even after a previous infection.

Norovirus: Symptoms

Norovirus infection usually progresses quickly and severely. Most patients experience severe vomiting and diarrhoea, usually accompanied by headache, abdominal pain, aching limbs and mild fever. These acute signs usually last one to three days. However, symptoms such as listlessness and a general feeling of illness may persist for a few days longer.

In individual patients, the norovirus infection causes only diarrhoea without vomiting or vomiting without diarrhoea. There are also infections that are completely without symptoms.

Through diarrhoea and vomiting the body can lose a lot of fluid and salts (electrolytes). This can be particularly dangerous for small children and older people: Circulatory problems, seizures and even kidney failure can occur.

You can read everything important about the typical signs of a Norovirus infection in the article Norovirus – symptoms.

Norovirus: incubation period

The norovirus incubation period (infection period) is the time between norovirus infection and the onset of the first symptoms. It varies slightly from person to person. In most patients the first symptoms appear within a few hours after infection. In others, one to two days pass between infection and the outbreak of the disease. In total, the norovirus incubation time can be six to 50 hours.

Caution: Those who have become infected with noroviruses are already contagious for others during the incubation period – i.e. even before the first symptoms appear. The risk of infection becomes even greater with the onset of symptoms.

Norovirus: examinations and diagnosis

If a norovirus infection is suspected, the family doctor is the right contact person. In order to detect the norovirus, three diagnostic steps are usually necessary: taking a medical history, physical examination and detection of the norovirus.

Collection of the medical history

During the so-called anamnesis, the physician inquires about the exact symptoms and other important parameters. Possible questions are:

  • Do you suffer from diarrhoea and vomiting?
  • Are you feeling weak and tired?
  • What did you eat in the last hours before the onset of the symptoms?
  • Have you had contact recently with people who have had similar symptoms?

Even the typical symptoms can be a very strong indication of an infection with noroviruses.

Physical examination

After the anamnesis, the doctor carries out a physical examination. He focuses on the abdomen: First, he uses a stethoscope to check whether normal bowel sounds are audible. Then he carefully palpates the stomach. He pays attention to tension (“defense tension”) and possibly painful areas in the abdomen.

The physical examination primarily excludes other causes of diarrhoea and vomiting.

Detection of noroviruses

There are several diseases that cause similar symptoms to a norovirus infection. A reliable diagnosis is therefore only possible by detecting the pathogens. For this purpose, a sample of stool or vomit is examined in the laboratory. So far this has only been possible in special laboratories.

There are several ways to detect noroviruses. One can either search for characteristic components of the viruses such as nucleic acids or proteins in the patient samples. Or they try to detect virus particles directly – with the help of an electron microscope.

Virus detection is important when there are a high number of cases of vomiting and diarrhoea in a given area or Community institution in a short period of time. Once noroviruses have been identified as the cause of the disease, suitable measures can quickly be taken to prevent the further spread of the pathogens.

Norovirus: obligation to notify

Proof of the norovirus is notifiable to the authorities. The data will be transmitted to the responsible health authority with the name of the patient.

The mere suspicion of a norovirus infection is notifiable if the person concerned handles food or works in communal catering facilities. The aim of the notification obligation is to detect local norovirus epidemics at an early stage and thus prevent further diseases.

Norovirus: treatment

There is no specific drug therapy for norovirus infection and it is usually not necessary. Instead, one tries to alleviate the symptoms as much as possible (symptomatic therapy).

In general, patients with Norovirus should take it easy. Bed rest is recommended. Further measures depend on the severity of the symptoms and the patient’s general state of health.

Norovirus treatment for mild to moderate symptoms

If an infection is only mild to moderate in severity, the patient can be cared for at home. The loss of fluid and electrolytes (sodium, chloride, potassium etc.) due to vomiting and diarrhoea should be compensated. For this purpose, the patient should drink plenty of fluids with sufficient salts. This can be water or tea with a little salt and sugar, broth and diluted juices. Infants and toddlers must be given more breast milk or an equivalent substitute.

Caution: Shifts in electrolyte values can be dangerous. For example, they can cause drowsiness, circulatory problems and cardiac arrhythmia.

Despite the diarrhoea, you should try to eat a little. This helps the intestinal mucosa to recover. For example, rusks, butter cookies and crispbread are easily digestible. Even after an infection has been overcome, one should initially only eat easily digestible food and avoid heavy, high-fat food.

Note: The household remedy “cola and pretzel sticks” is not suitable for vomiting and diarrhoea: The caffeine in cola can increase the loss of fluid. This is why cola is not advisable, especially for children. Salt sticks are not problematic in themselves. They supply electrolytes mainly with sodium, but not with potassium, which is also required. This is found in bananas, for example.

Norovirus treatment for more severe symptoms

In the case of pronounced norovirus signs, it can be useful to compensate for the loss of fluid and electrolytes with a so-called substitution solution from the pharmacy. This is especially true if the patient cannot or does not want to take in enough fluids and electrolytes. This often happens with children and older people.

The substitution solution is also called oral rehydration solution (ORL) or WHO solution (according to the World Health Organization WHO). It contains dextrose and electrolytes dissolved in water such as table salt or potassium chloride. They are available at the pharmacy, mostly in powder form to dissolve in liquid.

For stronger vomiting, a remedy for nausea and vomiting (antiemetic) can be administered in consultation with the doctor.

Norovirus treatment for severe symptoms

If the symptoms are severe and persistent, a Norovirus infection should definitely be treated in hospital. There, the doctors can compensate for the loss of fluid via an infusion into the vein. Necessary nutrients and electrolytes can also be administered quickly in this way. Often the patient is also given a remedy for strong vomiting (antiemetic).

Note: Children and the elderly are usually particularly sensitive to the high loss of fluids and electrolytes. In these patients, the norovirus therapy is therefore usually carried out in hospital.

Norovirus: pregnancy and infants

Pregnant women often worry a lot when they become infected with the Norovirus. The unborn child is not threatened by the noroviruses themselves. However, the violent vomiting and/or diarrhoea can build up so much pressure in the body that the contractions start early. In addition, it is particularly important for expectant mothers to always have an adequate supply of fluids, electrolytes and nutrients.

If a newborn or an infant falls ill with Norovirus, it can be very dangerous. Babies and toddlers are sensitive to the viruses, and fluid loss can quickly become life-threatening for them. Therefore, treatment is often carried out in hospital.

If an older child or an adult in a household falls ill with Norovirus, special care should be taken with hygiene when handling the infant. The sick person should be isolated as much as possible from the infant and other family members.

Caution: If infants show signs of Norovirus infection, a doctor should be informed immediately as a precaution.

Norovirus: course of disease and prognosis

An infection with the Norovirus is usually severe and short. The symptoms usually last one to three days. If no complications occur and the fluid and electrolyte balance is carefully balanced, Norovirus usually heals without any problems.

Children under six years of age should not return to a community institution (such as a kindergarten) until two days after the (suspected) norovirus infection has subsided. Careful attention must be paid to hygiene.

Especially in people who are older or weakened by other diseases (such as HIV), the norovirus course and duration of symptoms can be more severe. This often applies to infants and toddlers. Here, treatment in hospital may be necessary. This is especially true if the loss of liquid and electrolyte is very high. Then there is the danger that internal organs will be damaged. Only in very rare cases does Norovirus lead to death.

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Sandra Eades
Hello I am Sandra Eades, physician, researcher and author from Australia. I am working currently as researcher for a private institution. I have studied in Britain and Australia, where I currently reside. I write about research topics in the organization of the public health government agencies. For the iMS I write about general medical conditions. I also research scholar sources to provide information to writers of other articles. I also check the citations of scholar papers. Finally, I read other articles before they are published. I am also a mother of three children!