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Infection with many viruses will result in decades-long if not lifetime immunity, for example chicken pox.

Because of the large number of viruses responsible for the common cold, lifelong immunity to the common cold isn't possible; we will still be susceptible to those we haven't encountered before. But we do develop immunity to those we've been exposed to.

Influenza virus mutates quickly enough that there will nearly always be strains which will be new to us. Immunity to HIV is difficult because of the particular cells the virus attacks (as well as mutations).

However, Norovirus, while there are many strains, is particularly problematic because immunity to a strain lasts less than a year, making reinfection with the same strain repeatedly possible.

Is the reason Norovirus infection doesn't confer longer-lasting immunity known?

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    $\begingroup$ Your first question! :) interesting read +1, but I'm not able to answer it I'm afraid. And congratz with your moderatorship @Parents! $\endgroup$ – AliceD Apr 14 '15 at 2:17
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    $\begingroup$ @AliceD - I was researching this, and thought, "Wait! I know where I can ask!" ') Also, thanks. It's a great site. $\endgroup$ – anongoodnurse Apr 14 '15 at 3:48
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    $\begingroup$ I cannot answer this with anything but a guess, still: Some norovirus immunity seems to be caused by non-functional fucosyltransferase, which is (to keep it short) related to the ABH antigen. (see en.wikipedia.org/wiki/Norovirus) If (something similar to) a normal human antigen can confer immunity to norovirus, maybe the "real" norovirus antigen is so close to autoimmunity that our immune system filters a lot of them out. $\endgroup$ – skymningen Apr 14 '15 at 6:28
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    $\begingroup$ I am soooo going you have to come back to this when I have time. I'm currently struggling with the scope I want to include (mucosal immunity, IgG vs IgM, HRV serotypes, noro infectious dose...). If I want to dive deep into the biology here would it be better to repost the question there Q/A style, or can juat do it here? $\endgroup$ – Atl LED Sep 19 '15 at 1:08
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So the direct mechanisms of norovirus immunity aren't well understood - the shortage of straightforward animal models, and the extreme difficulty in culturing the virus make mechanistic studies really rather hard.

A modeling study pegged the duration of immunity at 4.1 to 8.7 years when talking about symptomatic disease, which is much higher than many of the estimate's you've encountered, and isn't actually all that fast. The older estimates were built off human challenge studies, which involved massive doses of norovirus, rather than the normal exposure you'd have. Now that is for a single strain, but immune cross-reactivity for strains isn't well understood. There's also several efforts to develop norovirus vaccines, which suggests some duration of immunity is at least possible. It's also possible that a proportion of the population (~20%) is simply immune due to the absence of the FUT2 gene, which acts as a receptor for the virus in the intestines.

In addition, there's definitely some antigenic drift, where mutations in the primary antigens negate previous immunity to the disease (the same mechanism that causes you to eventually lose immunity to a particular strain of influenza).

This paper is a pretty brief review of all these factors, written by some norovirus experts.

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  • $\begingroup$ Thank you! I was getting some impressions in my reading last night and touched on some of the topics, for example lack of cell cultures that will grow the virus, something that seems to be getting better) but was getting nowhere fast with "why". Thanks for the link!! $\endgroup$ – anongoodnurse Apr 15 '15 at 3:03
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    $\begingroup$ +1 I should point out, that my comment that I want to come back with an answer to this question is not because of a disagreement with anything here. Having worked on a culturing system for norovirus, I just have a lot of opinions on the matter. There are no italics extreme enough to to be apllied to the extreme difficulty in culturing, but I really appreciate that note :) $\endgroup$ – Atl LED Sep 19 '15 at 1:15
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    $\begingroup$ @AtlLED Nothing bad ever happened by having a subject matter expert provide an answer with more detail :) $\endgroup$ – Fomite Sep 19 '15 at 18:38

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