Norovirus causes more than half of all food-borne illnesses in the United States, and is the second greatest source of reported food borne illness outbreaks in the European Union. A norovirus is a small virus that contains RNA and is surrounded by a protein coating. By sequencing the RNA, scientists have discovered that there are many different types of norovirus. Originally, strains were named based on the city in which they were first identified. Thus, one common strain used to be called Norwalk virus. Based on genetic typing, we now know that there are at least 25 different strains of norovirus that affect humans.
Norovirus is transmitted mainly fecal-orally, and infected food handlers, contaminated water, and surfaces can be identified as important sources of transmission, which could further contaminate ready-to-eat foods, drinking water, shellfish, and fresh produce. A mere 10-100 virus particles are sufficient to transmit the disease.
The first sign of norovirus is usually a sudden sick feeling followed by forceful vomiting and watery diarrhoea. Some people may also have: a raised temperature (over 38C/100.4F), headaches, stomach cramps, aching limbs.
Symptoms usually appear one to two days after you become infected but they can start sooner. Most people make a full recovery within a couple of days.
Apart from the risk of dehydration, the illness is not generally dangerous and there are usually no long-lasting effects from having norovirus. However, it can be pretty unpleasant while you have it.
A recent study found that grape seed extract could reduce the infectivity of Norovirus surrogates.
Researchers from Ghent University, Belgium have shown that grape seed extract does so by denaturing the capsid protein, which is the coat of the virus, thereby disabling the virus.
In the study, the researchers observed that under treatment with grape seed extract, at low doses, the spherically-shaped murine (mouse) norovirus-1 coat proteins clumped, and showed obvious deformation and inflation. At higher doses, the researchers saw no coat proteins, only protein debris. This provides evidence that grape seed extract could effectively damage the norovirus capsid protein, which could reduce viral binding ability and infectivity accordingly.
The researchers used surrogate viruses because there are no suitable animal models of norovirus, and human norovirus has been impossible to propagate in cell cultures. The surrogate virus, murine norovirus-1, can be grown in cell culture, and belongs to the same genus as human norovirus, and has a very similar genome structure, and morphology. Nonetheless, the researchers were able to measure the specific binding strength of human norovirus by two different methods, finding that it declined precipitously under the influence of grape seed extract, providing further support to their results.