Vomiting diarrhea: One in five people has noroviruses

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MunichSudden diarrhea and acute vomiting - a gastrointestinal infection often comes out of the blue. In around 20 percent of cases, the culprit is a norovirus, a recent study shows. The result confirms the importance of developing a vaccine against the virus.

There are many pathogens that disturb the human digestive system - from salmonella to rotaviruses. But hardly any other pathogen causes the hasty search for the quiet place as often as the norovirus. In 18 percent of cases, the viruses are responsible for acute gastrointestinal complaints. That's what Dr. Benjamin Lopman and his colleagues at the Centers for Disease Control and Prevention (USA). Their investigation was based on data from 175 studies from 48 countries in which over 187,000 cases of gastroenteritis had been documented.

Already 18 viruses make you sick

Noroviruses are transmitted from person to person through contaminated food, water or dirty surfaces. The high infectivity that characterizes the norovirus is particularly insidious: "Even 18 viral particles are enough to infect a healthy person," explains Lopmann. For comparison: a single gram of a patient's stool sample contains over a billion viruses. In addition, an infected person is contagious to others even if he himself has not yet felt anything of the unwanted guests in his digestive system.

Noroviruses often mild

However, the data also show that, despite the often very stressful symptoms of norovirus sufferers, the infection is usually mild. Only 17 percent of the patients who had to be treated in a hospital for gastrointestinal infections suffered from the norovirus. In most cases, these are very young, very old, or immunocompromised people.

The analysis also showed that the infections are not necessarily more common in developing countries. At least according to the data, the percentage there was 14 to 19 percent - in Western countries it was 20 percent. This could be an indication that the water or sewage supply apparently had no influence on the norovirus infections. In the case of other gastrointestinal germs, however, such measures have a measurable effect - for example in the case of cholera.

Due to their sheer mass and high contagion potential, noroviruses nevertheless cause many serious gastrointestinal infections. And especially in developing countries, diarrhea is one of the main reasons for the high child mortality. “We therefore still have to learn a lot about the norovirus in order to be able to control it,” said the researchers.

No immunity, no vaccination

An infection with the norovirus usually lasts for one to three days. If there are no complications, the ghost usually disappears again without permanent damage. However, many believe that they are immune to the disease after being infected with the norovirus. This is not the case because there are very large numbers of norovirus species that are constantly changing. This fact has so far destroyed all efforts to develop a working vaccination against the virus. However, there is one approach that is already in clinical testing. (lh)

Source: Ahmed S.M. et al. Global prevalence of norovirus in cases of gastroenteritis: a systematic review and meta-analysis; The Lancet Infectious Diseases, Early Online Publication, June 27, 2014; doi: 10.1016 / S1473-309970767-4

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