Norovirus structure (Copyright: BV Prasad)
“More than 80% of human norovirus genotypes were detected in oyster samples or oyster-related outbreaks,” said corresponding author Yongjie Wang, PhD. In the study, they 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% 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 due to coastal waters contamination by human waste. 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% of the US population, annually, resulting in ~20 million cases, including 56,000-71,000 hospitalizations and 570-800 deaths, according to CDC. Even touching a contaminated surface can result in infection.
Wang advise fully cooking oysters and other shellfish. He also urged development of a reliable method for detecting noroviruses in oysters, and a worldwide oyster-related norovirus outbreak surveillance network. http://www.eurekalert.org/pub_releases/2015-08/asfm-oht082815.php
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