The norovirus is in season: Why these pathogens are so dangerous


An infection with noroviruses norovirus causes gastroenteritis, an inflammation of the stomach and intestines, in humans. Ten virus particles are enough to infect a human being. This makes the virus one of the most infectious pathogens out there. Especially during the colder winter months, the number of gastrointestinal diseases caused by the virus rises rapidly.

The norovirus is considered the “perfect pathogen”: it is highly contagious and extremely resistant. A mere 10 to 100 virus particles are sufficient to cause an infection1. In addition, the virus can survive on inanimate surfaces for up to a week 2 and tolerates temperatures between -20 and 60 degrees Celsius1.

Patients suffer from nausea, abdominal pain, diarrhoea or vomiting for one to three days. Other individuals can easily become infected through smear infections. With each instance of vomiting or diarrhoea, affected patients excrete tens of billions of pathogens, which can settle on door handles, furniture or hands. Theoretically, a single infected person could trigger a local epidemic.

####Winter is norovirus season

The norovirus season usually lasts from October to March in the northern hemisphere, and from June to September in the southern hemisphere.

The Centers for Disease Control and Prevention (CDC) estimate that noroviruses cause approximately 685 million infections worldwide each year, making them the most common cause of acute gastroenteritis worldwide. The viruses are responsible for every fifth case of acute gastroenteritis, which leads to diarrhoea and vomiting. Around 200 million of those affected are children under the age of five. About 200,000 patients die from the virus every year, including about 50,000 children, mainly in low-income countries.

Since 2002, the so-called GII.4 strains (genogroup II genotype 4) have caused most norovirus outbreaks worldwide, according to the CDC. However, in recent years other strains (such as GII.17 or GII.2) have replaced the GII.4 strains as main triggers in several Asian countries.3

Studies have also shown that the vigorous spread of noroviruses in Germany in the winter of 2016/17 was associated with a new virus variant.4 In total, 40 to 50 per cent of these norovirus diseases were caused by a new virus type (GII.P16-GII.2). It has also appeared in other countries such as France, Australia, Japan and China. In the past 2017/18 season, the figures returned to an average value.

Experts estimate the cost caused by noroviruses worldwide at $60 billion. The expenses are mainly due to health care costs and productivity losses.4

Recently, researchers led by Dr. Nihal Altan-Bonnet of the National Heart, Lung, and Blood Institute (NHLBI) in Bethesda, Maryland, USA5 discovered a mechanism that could explain why the viruses are so contagious: They apparently form clusters and hide in membrane vesicles – similar to hiding in a Trojan horse – to escape the body’s own defence system.

The RKI updates the norovirus figures weekly7.

Hand hygiene is the best prevention

Although researchers are searching intensively for a vaccine against noroviruses, there is still no preventive vaccination available. In practice, it is therefore all the more important to disinfect one’s hands regularly between patient contacts, as well as surfaces in the vicinity of the patient – as self-protection and for the benefit of the patients. The required spectrum of action is limited virucidal PLUS or virucidal. The use of an antiviral disinfectant is recommended when dealing with patients who are already ill. This prevents the virus from spreading further.

Further informationen

  1. Norovirus-Gastroenteritis, RKI guidebook (German)

  2. How long do nosocomial pathogens persist on inanimate surfaces? A systematic review, BMC infectious diseases

  3. Norovirus Worldwide, Centers for Disease Control and Prevention

  4. EpidemiologischesBulletin, 07/17, Robert Koch Institut

  5. Vesicle-Cloaked Virus Clusters Are Optimal Units for Inter-organismal Viral Transmission, Cell Host & Microbe, August 2018

  6. EpidemiologischesBulletin, 46/18, Robert Koch Institut

  7. EpidemiologischesBulletin, Robert Koch Institut

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