Understand that norovirus encompasses a large family of viruses that look and act like that picture Doug has down there. There are many different strains and I think 5 groups. Some cause illness in humans and many do not. The only thing I think might be somewhat unique are the adenoviruses that cause gastrointestinal symptoms. I think all the calciviruses and coronaviruses still fit under the noro umbrella. I think the other viruses are pretty rare and perhaps less virulent.