For three quarters of English-Grown Oysters contain the norovirus, a bug that causes diarrhea and vomiting, according to new research published Tuesday by the Agency of the Food Standards Agency (FSA). But health experts have warned the government that their tests did not reveal the extent of norovirusinfection, the tension that makes people sick. Neither could sayhow the various effective treatment processes before and after the harvest was to get rid of the virus, explaining that their studywill contribute to a Europe-Wide Review of the problem. Thetwo-year study looking at samples from 39 areas of oysterharvests across Britain found 76 percent away from the oystersdirectly from the bed contained the norovirus. "It is difficult to assess the potential health impact of these findings, because theresearch techniques available can not differentiate betweeninfectious and material non-infectious norovirus in oysters," theFSA said in a statement.