I'm a little confused on this subject. I have read NUMEROUS of articles and nothing seems to explain it that well. I know norovirus mutates, but how often? I've ready several times that "new strains are constantly emerging." and "the virus makes new strains all the time." Does this mean their are like millions of strains out there? I know the sydney strain is dominant right now but does that mean their are more? Does every person it passes through, mutates? Sorry so many questions I'm just so confused. We just had a sv* 2.5 weeks ago and I read you are immune for about 14 weeks. Is that true as well? So I could be right with someone who has noro and not get sick? Thanks!!!!