Oysters harbor, transmit human norovirus: Avoid raw ones

 

Oysters not only transmit human norovirus; they also serve as a major reservoir for these pathogens, according to research published August 28 in Applied and Environmental Microbiology, a journal of the American Society for Microbiology. "More than 80 percent of human norovirus genotypes were detected in oyster samples or oyster-related outbreaks," said corresponding author Yongjie Wang, PhD. "The results highlight oysters' important role in the persistence of norovirus in the environment, and its transmission to humans, and they demonstrate the need for surveillance of human norovirus in oyster samples," said Wang, who is Professor in the College of Food Science and Technology, Shanghai Ocean University, Shanghai, China. In the study, the investigators downloaded all oyster-related norovirus sequences deposited during 1983-2014 into the National Center for Biotechnology's GenBank database, and into the Noronet outbreak database. They conducted genotyping and phylogenic analyses, and mapped the norovirus's genetic diversity and geographic distribution over time. In earlier research, the investigators found that 90 percent of human norovirus sequences in China came from coastal regions. The current research showed that the same is true all over the world, except in tropical regions, from which sequences are absent. Oysters's status as reservoirs and vectors for human norovirus transmission is likely abetted by their presence in coastal waters, which are frequently contaminated by human waste, said Wang. Previous research suggests that noroviruses can persist for weeks in oyster tissues, and commercial depuration fails to expunge them. Norovirus causes stomach pain, diarrhea, nausea, and vomiting. It is extremely contagious, and infects more than 6 percent of the US population, annually, resulting in around 20 million cases, including 56,000-71,000 hospitalizations and 570-800 deaths, according to the Centers for Disease Control and Prevention. Even touching a contaminated surface can result in infection. Wang advised that people who eat oysters and other shellfish should eat them fully cooked, and never raw. He also urged development of a reliable method for detecting noroviruses in oysters, and a worldwide oyster-related norovirus outbreak surveillance network. Story Source: The above post is reprinted from materials provided by American Society for Microbiology. Note: Materials may be edited for content and length. Journal Reference: Yongxin Yu, Hui Cai, Linghao Hu, Rongwei Lei, Yingjie Pan, Shuling Yan, and Yongjie Wang. 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 American Society for Microbiology. "Oysters harbor, transmit human norovirus: Avoid raw ones." ScienceDaily. ScienceDaily, 28 August 2015. <www.sciencedaily.com/releases/2015/08/150828135213.htm>.

Lemon juice disinfects against human norovirus

 

Noroviruses are the predominant cause of gastroenteritis outbreaks in community settings such as hospitals, cruise ships, and schools. The virus is extremely contagious and is mostly transmitted via "fecal-oral-route," i.e., through contaminated hands or contaminated food. Symptoms include violent and sudden onset of diarrhea, vomiting, and nausea. "It is therefore important to provide a safe and harmless disinfectant against human norovirus," explains Grant Hansman, head of CHS junior research group at the German Cancer Research Center noroviruses and the University of Heidelberg. The group is funded by the CHS Foundation. Some older observations found that fruit extracts, such as orange or pomegranate juice, could reduce the infectivity of surrogate noroviruses. This current study was a continuation of an earlier project conducted at the National Institutes of Health in the United States, where they discovered that citrate from a commercial company could bind to the norovirus capsid protein. "However, it was only by chance that this discovery was made, like a lot of scientific research, but it turns out to be very interesting." Dr Hansman explains. Human noroviruses does not grow in cell culture, so they tested the effects of increasing concentrations of citric buffer on the so called norovirus virus-like particles, which have the same surface characteristics as real viruses. Dr Hansman and his staff show that the virus particles change their shape after citrate binding. X-ray crystal structures revealed that the citrate -- from lemon juice or citrate disinfectants -- precisely interacts at the binding pocket on the particle that is involved in attaching to host ligands -- the so-called histo-blood group antigens. These new results may explain why citrate reduces the infectivity of noroviruses. "Maybe a few drops of lemon juice on contaminated food or surfaces may prevent the transmission of these viruses," speculates Hansman. With his staff, he now plans to investigate if citric acid could reduce symptoms in those already infected with noroviruses. Story Source: The above post is reprinted from materials provided by German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ). Note: Materials may be edited for content and length. Journal Reference: Anna D. Koromyslova, Peter A. White, Grant S. Hansman. Treatment of norovirus particles with citrate. Virology, 2015; 485: 199 DOI:10.1016/j.virol.2015.07.009

Noroviruses cause around a fifth of all cases of acute gastroenteritis worldwide

 

June 26, 2014

The Lancet

Noroviruses are a leading cause of acute gastroenteritis (diarrhea and vomiting) across all age groups, responsible for almost one-fifth of all cases worldwide. New estimates highlight the importance of developing norovirus vaccines, say the authors. "Our findings show that norovirus infection contributes substantially to the global burden of acute gastroenteritis, causing both severe and mild cases and across all age groups. Diarrhea remains one of the leading causes of death of children in developing regions of the world."

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Noroviruses are a leading cause of acute gastroenteritis (diarrhea and vomiting) across all age groups, responsible for almost a fifth (18%) of all cases worldwide. New estimates, published in The Lancet Infectious Diseases, highlight the importance of developing norovirus vaccines, say the authors.

"Including data from 48 countries and involving more than 187,000 gastroenteritis cases worldwide, these new estimates are the largest analysis of norovirus infection and disease to date. There has been a proliferation of research on norovirus globally in the last five years, and we harnessed that data for this study," says lead author Dr Benjamin Lopman from the Centers for Disease Control and Prevention in the USA.

"Norovirus spreads from person to person and through contaminated food or water and contact with contaminated surfaces. The virus is so contagious that as few as 18 viral particles may be enough to infect a healthy person, while more than a billion viruses can be found in a single gram of an infected person's stool. Currently, there is no vaccine or treatment for norovirus."

Lopman and colleagues analysed 175 published reports to compile data on the prevalence of norovirus in individuals with acute gastroenteritis between 1990 and 2014. They found that norovirus tended to be more common in cases of acute gastroenteritis in the community (24%) and outpatient (20%) settings than in emergency department visits and hospitalisations (17%), supporting the notion that norovirus is a more common cause of mild disease. However, because of its sheer frequency, norovirus causes a substantial amount of severe disease.

Norovirus was also found in a considerable proportion of cases of acute gastroenteritis cases in both developing countries (14-19%) and developed countries (20%). "This highlights that norovirus, unlike bacterial and parasitic pathogens, cannot be controlled just by improved water and sanitation," explains Lopman.

He concludes, "Our findings show that norovirus infection contributes substantially to the global burden of acute gastroenteritis, causing both severe and mild cases and across all age groups. Diarrhea remains one of the leading causes of death of children in developing regions of the world. We have much to learn about norovirus in those settings, and how it can best be controlled."

Writing in a linked Comment, Dr Ulrich Desselberger and Professor Ian Goodfellow from the University of Cambridge in the UK say, "Inconsistent age stratification across studies prevented an indepth analysis of the burden in people older than 65 years, typically more susceptible to complications and at a greater risk of norovirus-associated death. Furthermore, many countries have not studied the prevalence of noroviruses in sufficient detail to gain reliable burden estimates. Most notably is the paucity of data from Africa where the effect of gastroenteritis probably has more severe consequences. Estimates suggest that 200,000 deaths per year happen in children younger than 5 years of age in developing countries. Therefore, additional high quality studies in these settings will be crucial to improve disease estimates."