Noroviruses hide in oysters

Luise Heine has been an editor at since 2012. The qualified biologist studied in Regensburg and Brisbane (Australia) and gained experience as a journalist in television, in the Ratgeber-Verlag and in a print magazine. In addition to her work at , she also writes for children, for example for the Stuttgarter Kinderzeitung, and has her own breakfast blog, “Kuchen zum Frühstück”.

More posts by Luise Heine All content is checked by medical journalists.

Oysters are considered a delicacy. But real gourmets, who prefer to eat them raw, quickly catch noroviruses. The nasty gastrointestinal pathogens end up in a strange detour in the shellfish's body.

Abdominal pain, explosive vomiting and severe diarrhea - anyone who suffers from these symptoms and slurped a few oysters a few hours earlier may have become infected with noroviruses. The origin of the viruses are not the marine animals themselves, but - humans. Chinese researchers have now found out. Yongjie Wang and his team from Shanghai Ocean University report that the oysters can not only transmit the highly contagious viruses, but also serve as a reservoir for the pathogens.

Worldwide, norovirus outbreaks occur again and again in connection with the consumption of oysters. In many cases, the genetic composition of the virus is determined and archived in an international database. It was precisely these archives that Wang and his colleagues now resorted to. They examined the genetic information of the pathogens that had been stored there between 1983 and 2014 and compared how similar it was with the viruses of the different age groups. The researchers also recorded the geographical distribution of the individual virus sub-forms.

Origin: man

It was important to realize that 80 percent of the viruses in the oysters came from humans, as revealed by certain parts of the virus' genetic code. "The oysters not only serve as a transmission path for the viruses, they also persist in their tissues for a long time," the scientists write. In this way, the animals would become a place of retreat for the viruses, from where they could infect people again and again.

“Oysters mainly live near the coast. But it is precisely there that people's sewage containing goth is discharged into the sea in many places, ”explains Wang. From a Noro outbreak in 1993 it is even recorded that fishermen who had noroviruses relieved themselves in the water. Human excrement is usually a good “fertilizer” for marine animals, but it carries the risk of contamination with pathogens such as noroviruses.

Do not consume raw

The scientists advise those who still do not want to forego the consumption of shellfish should not consume oysters and other mussels raw. In fact, food has to be heated to over 60 degrees in order to render norovirus harmless.

Source: Yongxin Yu et al. Molecular epidemiology of oyster-related human noroviruses: Global genetic diversity and temporal-geographical distribution from 1983 to 2014. Appl. Environ. Microbiol., 2015 DOI: 10.1128 / AEM.01729-15

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