Would the h1n1 test show positive after being sick?
June 25, 2009 9:38 AM   Subscribe

Would an h1n1 test show a positive result on a person that had the flu weeks ago but is not currently sick?

I am curious how the test works. I am pretty sure that viruses stay in our bodies forever, even after we get better. Would the test show the virus even though you're no longer sick or contagious?

posted by flyingcowofdoom to Health & Fitness (4 answers total)
SOME viruses stay in your body forever, but not all. Influenza A (i.e., "the flu") won't persist forever. You will still have a few viruses around for a while after symptoms are gone, but eventually flu clears entirely (as opposed to other viruses like retroviruses [HIV], herpes viruses [herpes, chicken pox], etc., which actually remain in your cells indefinitely).

As far as testing positive, I'm not sure what the test they are using is. If it actually looks for viral particles, it will be negative once you get better. If, on the other hand, the test looks at specific anti-H1N1 antibodies, then the test would remain positive, and you can differentiate active versus previous infection based on the type of antibodies (I doubt they use that sort of testing for flu).
posted by davidnc at 10:00 AM on June 25, 2009

I'm not an expert on any of this, but here's how I understand it: Biologists / pathologists / polymaths, please correct any errors.

Some viruses do stay in our bodies forever, but others do not. They do this by stopping or drastically dialing back reproduction and hanging out in like the nerves or something where the immune system doesn't spend so much time.

Chicken pox (Varicella zoster virus) does this, and sometimes has a later outbreak which is called Herpes Zoster or Shingles or whatever. I think it's common in retroviruses?

Anyway, even if the virus is gone, your immune system is changed by learning to fight it, and some tests will detect that.

I know that early on a lot of the early H1N1 tests used PCR (described near the end of this), which necessarily means having active virus genetic material handy. It looks like new virus testing technologies are being developed because of swine flu. I guess those you need to have active viruses reproducing in your nasal passages for it to work. I think H1N1 does not go latent, and people do eliminate it completely from their systems (though how long it takes from when symptoms go away I don't know). Thus these tests will not indicate swine flu.
posted by aubilenon at 10:01 AM on June 25, 2009

I wouldn't think 2 weeks would be enough for the immune system to completely eliminate all viruses.
posted by Chocolate Pickle at 11:05 AM on June 25, 2009

Indeed, H1N1 won't go latent. None of the orthomyxoviruses (the type of viruses that includes Influenza A) are capable of that.

They could theoretically stay around in the body if they aren't cleared, but that would only occur if there were some sort of antibody deficiency (an agammaglobulinemia with no antibodies, inability to make memory cells, etc.), but I would guess that in that case influenza would likely be fatal... then again, you could try to clear it with antiviral therapies, which is I suspect what's done for people with those conditions.
posted by davidnc at 1:09 PM on June 25, 2009

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