Norovirus infection: contagion, symptoms, treatment

Diarrhea, vomiting, and nausea are typical symptoms of a gastrointestinal infection caused by noroviruses. What then helps and how to prevent infection

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Briefly explained: what are noroviruses?

Noroviruses cause gastrointestinal infections (gastroenteritis, gastrointestinal flu). Typical symptoms are nausea, vomiting, abdominal pain and diarrhea. The pathogens are highly contagious. This is why they spread particularly easily when many people come together in a small space - for example in kindergartens, schools, clinics and old people's homes.

It sometimes only takes a few hours from infection to the outbreak of the norovirus infection. The disease is unpleasant, but rarely life-threatening. It is important to replace lost fluids and minerals. The vomiting diarrhea usually passes after a few days. However, there can also be complications in children, elderly or weakened people. There is no medication or vaccination against the noroviruses. The best prevention is good hygiene.

Contagion: how is the norovirus transmitted?

Noroviruses are widespread worldwide and are relatively resistant: They sometimes survive for days on objects such as towels, doorknobs, taps or toilet seats and flushes. They can survive well in food - even if they are chilled or pickled. They can even withstand temperatures of up to +60 degrees Celsius for several minutes.

Less than ten noroviruses can make you sick. Most of the time, you pick up the pathogen through direct human-to-human contact, for example when shaking hands. The viruses then easily get from the hand into the mouth. You can also become infected through contaminated objects or foods such as salads, berries, raw mussels or contaminated drinks.

Sick people excrete the pathogens in large numbers with the vomit and through the stool, the latter possibly even before symptoms appear. When vomiting, noroviruses can also be trapped in tiny droplets and spread a little way through the air.

The cases of illness often accumulate in the winter months. Lower temperatures, rain, and low to moderate humidity, such as those found in winter, increase the likelihood of outbreaks. Researchers suspect that the causes are better stability of the virus, more interpersonal contacts and a poorer immune system.

Incubation period: when does the disease break out?

The time from infection to symptoms occurs is usually a few hours to about two days after infection.

What are the symptoms of a norovirus infection?

The disease usually starts very suddenly with nausea, severe vomiting, abdominal cramps and diarrhea. Those affected feel miserable, weak and dizzy. A slight fever, headache and body aches are common accompanying symptoms.

The infection can take different courses. The acute phase usually subsides two to three days later. Depending on the patient's constitution, it may take longer or cause only slight discomfort. Usually the disease heals without any consequences.

Is Norovirus Infection Dangerous?

The organism loses a lot of fluids and salts through vomiting and diarrhea. They need to be replaced. The loss of fluid is particularly dangerous for children and the elderly or weak people. They can dry out quickly and life threateningly.

If in doubt, a doctor should be consulted too soon rather than too late. If necessary, he can supply the missing liquid via a drip. In severe cases, hospitalization is required.

Diagnosis: How is a norovirus infection diagnosed?

The diagnosis can often be suspected based on the typical course and symptoms. If in doubt, a stool sample from the patient is examined for pathogens. Since this can take a while, it is important to start hygiene measures as soon as there is an urgent suspicion so as not to lose time.

If noroviruses are detected, there is an obligation to report to the health department according to the Infection Protection Act. Public institutions such as hospitals and old people's homes must also report when acute gastrointestinal infections increase.

Treatment: what can I do if I have a norovirus infection?

There is no specific remedy for the pathogen. Only the symptoms can be alleviated.

In the case of a norovirus infection, it is particularly important to replace the fluid that has been lost. Those affected should drink enough. Because diarrhea and vomiting deprive the body of plenty of water and salts (electrolytes).

For example:

  • Special electrolyte mixtures from the pharmacy. They are mixed with water and replace salt and liquid in optimal concentration.
  • Diluted juices
  • broth
  • Tea with a little sugar and salt

Despite the nausea, the sick should try to eat a little too - preferably easily digestible carbohydrates such as rusks or white bread. The affected intestinal mucosa can then recover better.

Norovirus Infection: How Long Are You Contagious?

Even after the symptoms have subsided, there is still a risk of infection for at least two days. Even after that, consistent hand and toilet hygiene is important for two weeks. Because the viruses remain in the stool for up to two weeks after infection, in some cases even longer.

To prevent the disease from spreading in communal facilities, strict hygiene rules and the following rules apply:

  • People who deal with food at work must be released from work for at least two days after the symptoms have subsided, otherwise they may contaminate food and become a source of outbreaks. You must also pay special attention to hand and toilet hygiene for four to six weeks.
  • Children under the age of six are only allowed to go back to kindergarten or crèche after they have been symptom-free for two days. A medical certificate is not required, but here too, hygiene should continue to be observed.
  • People who are employed in health or community facilities should return to their workplace two days at the earliest after the symptoms have subsided. Here, too, what has been said about hygiene applies.

How can you prevent a norovirus infection?

Norovirus infection does not lead to relevant immunity. Anyone who has survived the disease can become infected again. Similar to flu pathogens, noroviruses are extremely versatile. They are available in numerous variants.

Hygiene rules: This is how the risk of infection can be reduced

  • Always wash your hands thoroughly with soap after every visit to the toilet, before eating and before touching your mouth (for smokers: also before smoking), especially in public places. Here in the video you will learn how to wash your hands properly.
  • Clean foods like fruits and lettuce carefully, especially if they are eaten raw.
  • Cook food thoroughly.
  • Anyone who picked up the virus should reduce contact with others to a minimum for a few days (at least two days after the end of the acute phase).
  • Even if you suspect a norovirus infection, you should keep your distance from sick people and those with weakened immune systems. To avoid spreading it to others, medical and food workers should seek advice from a doctor. According to the Infection Protection Act, they may not be allowed to work temporarily.
  • Sick people should definitely use their own towels and personal care items and - if feasible - their own toilet. Dishes should be cleaned in the intensive program in the dishwasher or scalded after washing.
  • When caring for someone who is ill, you should pay special attention to their hand hygiene, especially if they have been exposed to vomit or stool. Hand washing is only partially effective due to the high number of excreted pathogens and the high level of infectivity. It is best to prevent your hands from getting dirty by wearing disposable gloves (wash your hands afterwards anyway!) And / or get a hand disinfectant that is effective against noroviruses from the pharmacy. Ask for a hand disinfectant that has the "limited virucidal plus" or "virucidal" effective range - with this you can detect not only noroviruses, but also many other diarrhea pathogens.
  • It is best to clean contaminated surfaces with disposable wipes, which you then dispose of. In this case, it is beneficial to use a disinfecting cleaner, for example based on chlorine or oxygen.
  • If possible, you should wash the sick person's bedding, towels and clothes at at least 60 degrees Celsius. The same applies to clothing that you wear when caring for sick people. A cotton apron is practical to protect clothing. For sensitive clothing, it is advisable to add disinfecting additives (bleaching), which support cleaning even at lower temperatures.

The recommendations also apply for a while if the person concerned feels good again, because he excretes noroviruses in his stool for another two weeks.

Experts advise taking the disease seriously. Because it provokes a number of stoppages and thus costs. It can actually be threatening for young children and the elderly. Medical treatment may also be necessary in young, healthy people. Nevertheless, the overall probability of dying from a norovirus infection is low: it is around 0.1 percent of all cases.

Professor Dr. Nils-Olaf Huebner

© W & B / private

Consulting expert

Professor Dr. med. Nils-Olaf Hübner, specialist in hygiene and environmental medicine, is the senior hospital hygienist at the University Medical Center Greifswald. He is a board member of the German Society for Hospital Hygiene and a member of other specialist societies and committees. As part of "AHOI-Patient im Boot", he and his team are researching the active involvement of patients, those in need of care and relatives in infection prevention.


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Important NOTE:
This article is for general guidance only and is not intended to be used for self-diagnosis or self-treatment. It cannot replace medical advice. Please understand that we do not answer individual questions.