Introduction
The Norovirus is next to the rotaviruses one of the most important pathogens of diarrhoeal diseases, which are not caused by bacteria. Among the viruses, the norovirus belongs to the so-called caliciviruses and is derived from the Norwalk viruses, named after the place of their discovery. There are many types of noroviruses that can cause infections in cattle, pigs or mice as well as in humans.
The gastro-enteric flu so typical of humans is caused by the human norovirus, which only affects humans. Noroviruses are spread worldwide and are considered to be very resistant to environmental influences. For example, they can easily survive temperature fluctuations between -20°C and +60°C. In experiments, they have shown a survival time of twelve days on infested surfaces (door handles, carpets, fittings …) and can also survive for a few days on raw food and in contaminated water.
Structure of the Norovirus
The Norovirus, like all viruses, does not have its own metabolism and is therefore dependent on other cells to survive and multiply. Therefore it attacks cells of the intestinal mucosa, which are called host cells after their infestation. The norovirus is about 35-39 nm thick (35 millionths of a millimeter) and has a twenty-faceted envelope.
In its interior, it consists only of proteins and the genetic information in the form of RNA, which it needs for reproduction. The RNA is later introduced into the RNA of the host cell, whereupon the infected cell produces proteins for the virus. From the finished proteins and RNA, new viruses are finally formed, which, once released, infect other cells. A cycle of mass-producing viruses and dying host cells is set in motion.
Transmission of the Norovirus
The Norovirus is extremely easy to transmit between humans compared to other viruses. Only 10 to 100 virus particles are sufficient to cause illness, which is why waves of disease often spread within a few days. One speaks of an infection when the virus enters the body and multiplies.
This does not necessarily mean that there is direct contact with an infected person, because the infection can also be spread by a so-called smear infection. For example, just touching contaminated objects (e.g. door handles) and food can be sufficient for transmission. The virus can survive for several days on objects and surfaces and is even resistant to some disinfectants.
Infection often occurs through the absorption of the virus via mouth or nose. One speaks of a fecal-oral transmission. This can happen, for example, if you do not wash your hands thoroughly after going to the toilet and eat something.
The viruses are not only spread during the acute illness, but can be detected up to 14 days after the end of the illness. Hygiene in dealing with those affected is therefore still an important component in the period after the infection to prevent further infection. Once the virus has been absorbed, the typical diarrhea of vomiting occurs within 10 hours to two days.
During this time the intestinal cells are attacked and after sufficient damage and own reproduction the typical signs of the infection with the Norovirus appear: These are defence methods of our body by which it wants to get the pest out of the body as quickly as possible before it attacks further intestinal cells.
- Nausea
- Vomiting
- Diarrhea
Norovirus infection occurs from person to person and in most cases faecal-oral. Through intensive body contact and droplet infection, as in kissing and sexual exchange of body fluids, the probability of becoming infected with the Norovirus is high.
The Norovirus is therefore also sexually transmissible. The Norovirus is a highly infectious gastrointestinal virus. Affected persons are already infectious for other people during the incubation period.
The risk of infection lasts from several days to two weeks. This means that infected persons are still infectious when their symptoms have already subsided. To infect others, 10 to 100 virus particles are sufficient. Infected persons rarely remain permanently excreted. This means that they excrete noroviruses with every bowel movement for months or years and can thus be contagious.
