Gastrointestinal infection by noroviruses

Noroviruses are widespread throughout the world and are responsible for the majority of non-bacterial gastrointestinal infections. The viruses are highly infectious. This explains the very rapid spread of infections in places such as care homes, hospitals, kindergartens or also cruise ships, for example.

At a glance

  • Noroviruses are highly infectious.
  • The viruses cause great gastrointestinal discomfort with severe diarrhea and vomiting.
  • As patients quickly lose a lot of fluid, they should drink plenty.
  • Noroviruses can spread very rapidly in places such as care homes, hospitals, kindergartens or also cruise ships, for example.
  • Good hygiene measures are vital in stopping and preventing infection.

Note: The information in this article cannot and should not replace a medical consultation and must not be used for self-diagnosis or treatment.

Norovirus: blood test test tube with a sticker for a positive norovirus test.

What are noroviruses?

Noroviruses cause acute gastrointestinal discomfort, characterized by waves of severe vomiting and bad diarrhea.

The norovirus was originally named after the town of Norwalk in Ohio, because in 1968 there was a major outbreak in an elementary school there. The term “norovirus” was introduced in 2002.

30% of diseases in children are caused by the norovirus. The figure is as high as 50% for adults.

Noroviruses are responsible for the majority of non-bacterial gastrointestinal infections. In children they cause around 30 percent, and in adults up to 50 percent, of illnesses that have to be reported. Children below the age of 5 and people over the age of 70 are particularly often affected.

What symptoms do noroviruses cause?

Noroviruses cause sudden gastrointestinal infections with waves of severe vomiting and bad diarrhea. These symptoms can lead to a dangerous loss of fluids. Some infected people only suffer from vomiting or only from diarrhea.

Patients usually feel very ill and weak. They suffer from stomach pain, nausea, and head and muscle aches. The body temperature can be slightly elevated, but high temperatures are rather rare. The symptoms usually fade away after 1 to 2 days.

What causes norovirus infections?

Noroviruses are only transmitted from person to person. As the viruses often change their genetic properties, there are many different variants. They are currently divided into 5 main groups. Only groups I, II and IV are significant to human beings. Most infections in adults are triggered by type IV viruses.

The viruses are excreted via the stool and vomit. The risk of infection is very high: it is estimated that just 10 to 100 virus particles are enough to infect someone. This occurs through skin contact with infected surfaces such as door handles, or by breathing in droplets containing the virus that get into the air through vomiting. This is also the reason why noroviruses can spread very quickly in homes for the elderly, hospitals, and community facilities.

But infections can also originate in foods. In particular, raw foods like salads, crabs or mussels, and drinks can be infected with noroviruses.

How common are norovirus infections?

Noroviruses are widespread around the world. Infections may occur throughout the year, but they are frequently seen between October and March.

How does the illness progress after a norovirus infection?

The time between becoming infected and the first symptoms occurring is between 6 hours and 2 days. This period of time is known as the incubation period.

While they are acutely ill, infected people are highly contagious. However, the virus can still be excreted via the stool 7 to 14 days, or even weeks in exceptional cases, after an acute illness. So careful toilet and hand hygiene are required even after the symptoms have disappeared.

Is there a vaccination against noroviruses?

Vaccinations are being researched, but no suitable vaccine is yet available.

How is a norovirus infection diagnosed?

A stool sample is usually tested to provide evidence of noroviruses.

A diagnosis should be reached for all patients that have diarrhea or vomiting and when there is no other reason for the symptoms. When cases occur in community facilities, hospitals, and homes for the elderly, in particular, the diagnosis should be sought as quickly as possible.

Confirmed norovirus infections have to be reported to the health authorities.

How are norovirus infections treated?

There are no medications that act directly on the norovirus. So it is only the symptoms that are treated. As diarrhea and vomiting cause a substantial loss of fluids, this needs to be offset, so patients should drink a great deal. Children below the age of 5 and people over the age of 70 react with particular sensitivity to the fluid loss that can occur through vomiting and diarrhea.

In cases of severe vomiting, drugs can be given to counter the nausea.

When do medical specialists need to be consulted?

Infants, pregnant women, seniors, and the weak should be treated by a doctor, particularly if attacks of diarrhea are occurring frequently and/or lasting more than 2 to 3 days, and if there is also a high temperature or vomiting.

Important: It is unclear whether lemon juice can help against infection with noroviruses due to the acids it contains. As yet there are no scientific studies that show any such effect on humans.

What should patients look out for at home?

Sick people should rest and limit contact with others as much as possible. The following should also be observed:

  • With diarrhea and vomiting it is important to drink a lot.
  • To offset the loss of salts, electrolyte replacement drinks from a pharmacy might help. They contain salts, minerals, and glucose.
  • Sufferers should only eat foods that are easy to digest, and take on sufficient amounts of salt.
  • If possible, they should use a separate toilet for up to 2 days after recovering, and thoroughly wash their hands with soap and water after going to the toilet. This applies for up 2 weeks after the illness.
  • Vomit or stool residue should be cleaned up as soon as possible as it is highly infectious. The hands should then be washed thoroughly.
  • Clothing, bedding, washcloths and towels should be changed regularly and washed at 60°C.
  • The toilet, wash basin, door handles and floors should be cleaned regularly. Single-use cloths are ideal for this purpose. Disposable gloves provide additional protection against infection. Water and standard cleaning materials are normally sufficient.

What should community facilities look out for?

It is important that the general hygiene rules in community facilities such as homes for the elderly, hospitals, kindergartens, and canteen kitchens are followed properly.

To prevent transmission via food, dishes should be thoroughly cooked, in particular those involving seafood.

The spread of the viruses can be halted most effectively in the period between the occurrence of the first symptoms through to the first 48 hours after the symptoms have cleared up.

In community facilities, in particular, whenever there is reason for suspicion, suitable measures should be taken immediately, even if the diagnosis has not yet come back from the laboratory.

Measures to prevent infection, particularly in community facilities, are compliance with rules on hygiene and consistent hand hygiene, disinfection of surfaces, wearing of protective clothing and isolation of people affected.

The following additional hygiene measures are particularly recommended during the period with diarrhea and vomiting:

  • isolation of the people or groups of people who are ill
  • wearing gloves, aprons and face masks to prevent infection linked to vomiting 
  • good hand hygiene and hand disinfection
  • disinfection of surfaces, toilets, wash basins, and door handles in the proximity of patients

Use approved disinfection products which are labeled “begrenzt viruzid PLUS” or “viruzid”.

When can children return to kindergarten?

Children younger than 6 who are ill, or suspected to be ill, with a gastrointestinal infection caused by the norovirus should not attend kindergarten or nursery. This is only permitted 48 hours after the symptoms have cleared up.

Which occupational groups do particular rules apply to?

Anyone who is sick should not go to work in any food-related role, such as in a canteen kitchen. They can go back to work 2 days after the symptoms have cleared up at the earliest. Particular attention should be paid to good hand hygiene in the workplace during the following 4 to 6 weeks.

Reviewed by the German Society for Gastroenterology, Digestive and Metabolic Diseases (Deutsche Gesellschaft für Gastroenterologie, Verdauungs- und Stoffwechselkrankheiten e.V.) (DGVS).

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