I hope this is the right place to ask. I subscribe to several Stack Exchange threads, and regard them as the best internet forum for genuine and credible answers.

I spent last evening talking to friend, at an Amateur Radio Club, who told me he has recently recovered from the norovirus. I was demonstrating an oscilloscope to him, and he also handled the handbook. All this is now in the holdall I used to carry it to the Club. I took all the precautions I could, like washing my hands and not getting them near my lips, nose etc. So, my question is: how long should I wait before opening my holdall, to be sure any infection there is dead?


Well, for him the virus is already likely at minimum levels within his body. If he's recovered (pass the fever phase) then his immune system has already dealt with the majority of the viral bodies in his system, since the peak of the immune response comes after the peak of the viral infection density (ignore B):

graph from Nature Review: Immunology

How much of the virus was left in his system to actually spread is hard to guess. Sometimes infections never truly go away, but merely become undetectable by conventional testing. However, if we're to assume that there's at least some norovirus left to transfer to you then you should realize that the greatest chance for exposure has already come and gone.

The moment you were in the same room together, talking in close proximity, shaking hands (if you did), or generally being close is the most likely source of any infection you could have picked up. However, while most virii don't survive well outside of the body, the norovirus notably bucks that trend. The Hawaiian Department of Health (PDF) notes that the virus can definitely survive outside the body for several days on hard surfaces (though it will not grow), can survive being frozen, and that it only takes about 100 viral units to cause an infection (which could fit a few thousand times over on a grain of salt). Scientific American also notes that norovirus can survive for months or years in sources of drinking water.

What you've already done is pretty much what you should do to avoid infection. You've washed your hands, refraining from mucous membrane contact, etc.

Ultimately how long you should wait depends on where the norovirus currently resides. A week should be sufficient if all of the norovirus is contained on the book or on other surfaces that you're not making contact with. However, if it's already had contact with your skin or mucous membrane, then you're either already fighting it off or you're about to become ill. Unfortunately it's a lot easier to expose yourself than contain something you can't see, as the Mythbusters have done a good job of showing (Video).

In all likelihood if he was still infected enough to transmit the virus to other people by the time you two started handling the same equipment and you didn't use gloves, you've probably been exposed. However, exposure doesn't automatically mean you get sick. If you're not sick within a week afterwards, you've successfully fought it off. So, congratulations, perhaps!

  • $\begingroup$ Thank you @MCM very much for that comprehensive answer. A bit reassuring, but it seems that really I must just wait and see. As a supplementary question: is my wife at risk (she did not come with me) assuming I do not show symptoms? Unfortunately I do not have enough "reputations" to vote your answer up, as I would like to do. $\endgroup$ – Harry Weston Jan 4 '13 at 15:09
  • $\begingroup$ @HarryWeston - "Is my wife at risk if I don't show symptoms?" Yes. Whether or not you show symptoms after having contracted any infection depends on your immune system's response. If you've seen a similar strain (or the exact same strain) before, then there's every chance you won't show symptoms but still be a carrier. If your wife hasn't encountered the strain, she could still get sick and invoke the normal immune response. This is all contingent on whether or not the guy passed it on to you, though. $\endgroup$ – MCM Jan 4 '13 at 15:44
  • $\begingroup$ Thank you again @MCM, so it is just a question of wait and see, though much much better informed now. $\endgroup$ – Harry Weston Jan 4 '13 at 16:23

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