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PostPosted: Tue Jan 26, 2010 2:25 pm 
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http://news.xinhuanet.com/english/2010- ... 819889.htm

Would you say their tests are better than ours to have such knowledge?


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PostPosted: Tue Jan 26, 2010 10:33 pm 
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Not sure it's about testing, moreover, I would say that the human immune system is doing what it does when given the opportunity: acquiring natural immunity.

I'm almost positive I was exposed to it as a school teacher but was probably asymptomatic. Therefore, if I was exposed, I now have my own antibodies.

Am I correct in assuming that acquiring natural immunity (for the specific strain I caught of course) will provide the same cross protection as the shot would provide for in the case of future mutation?

So why the need for the shot?

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PostPosted: Tue Jan 26, 2010 11:59 pm 
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Quote:
Not sure it's about testing, moreover, I would say that the human immune system is doing what it does when given the opportunity: acquiring natural immunity.

I'm almost positive I was exposed to it as a school teacher but was probably asymptomatic. Therefore, if I was exposed, I now have my own antibodies.

Am I correct in assuming that acquiring natural immunity (for the specific strain I caught of course) will provide the same cross protection as the shot would provide for in the case of future mutation?

So why the need for the shot?


GA -- If you did get H1N1, you will probably have some antibodies to the strain you caught, but how high your antibody titer (how strong your immune response) was as a result of your infection is questionable. Some people will develop a strong antibody response, others not so much. There have been numerous reports of people who've had mild or even moderate H1N1 illness getting the virus again a second time. Their viral exposure was not sufficient to be protective against re-infection. An asymptomatic infection might likewise not produce an antibody titer sufficient to prevent you from contracting H1N1, if you get exposed again.

Re whether you'd have cross-protection for other (future) strains of flu as a result of (possibly) having gained immunity through natural infection with the virus will depend on how close those future strains/mutations are to the strain you caught. If the virus differs significantly, antigenically speaking, then cross-protection is unlikely, regardless of whether you obtained your immunity from H1N1 infection or H1N1 vaccination. If the virus is very similar antigenically, then cross-protection is possible, provided your original exposure was strong enough to produce a robust antibody response. The dose used in the pandemic vaccine was chosen because it produced a robust response in 80% or better of all those vaccinated. I know of no data indicating what percentage of unvaccinated individuals achieve the needed response via their asymptomatic natural exposure to the virus.

The other reason a vaccine might be preferable to gaining immunity the "old fashioned way" (via natural infection with the virus) is that natural infections usually entail several days of feeling pretty miserable and all the risks associated with the illness itself. You aren't guaranteed an asymptomatic infection by any means. :grin:


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PostPosted: Wed Jan 27, 2010 5:54 pm 
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MKey1, what is your viewpoint about asymptomaic infections? I've read a lot about it with swine flu, various articles etc claiming that there have been many such.

But I've never heard in previous regular flu seasons that people get regular seasonal flu without any symptoms.

It somehow doesn't make sense to me. If someone catches flu, doesn't that necessarily mean they'll have some symptoms? If the virus is replicating, wouldn't it always cause noticeable symptoms?


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PostPosted: Wed Jan 27, 2010 11:11 pm 
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BeWell --

You ask very good questions. There have no doubt been a significant number of asymptomatic infections and infections so mild that the person might have totally ignored their symptoms as insignificant (i.e. subclinical infections). For instance, it's possible that someone might have had nothing more than a slight runny nose for a few days and thought nothing of it...thinking it just seasonal allergies or something like that.

Asymptomatic infections have happened in the past with other influenza strains and that's well-documented, so this isn't something new to pH1N1, but nobody really knows exactly how many people might have had asymptomatic or subclinical infections without testing for antibodies to the virus and taking medical histories. One way we often find these asymptomatic prior infections is when a group of healthy people volunteers for a research protocol, like taking a new vaccine or testing a new medicine, and during the intake process a sample of their blood gets drawn and some of them are found to already have antibodies to the virus yet didn't report ever having been sick with it or having been previously vaccinated against it.

Quote:
If someone catches flu, doesn't that necessarily mean they'll have some symptoms? If the virus is replicating, wouldn't it always cause noticeable symptoms?


It is possible to have been exposed to a virus in a dose low enough that you don't have any symptoms. For each virus, there is a certain minimal exposure necessary to produce clinical illness. The exposure dosage needed to produce clinical disease varies from virus to virus and has been studied by scientists. You can do a search using the terms 'HID50' (Human Infectious Dose 50 = the human infectious dose of virus needed for 50% of people exposed to develop clinical disease) and 'influenza' if you want to know about the details for flu. What most people consider "catching the flu" is that you come down with the classic symptoms of flu, that you are sick. You aren't considered to have "caught the flu" (at least in the vernacular) if you were exposed to the flu virions but never got sick. In medicine, we use a distinction: colonization versus infection. You are said to be colonized with a pathogenic microorganism if that organism grows in your tissues without causing any signs or symptoms of illness. You are said to be infected with the pathogen if it causes tissue damage and illness. As an example, many people have staphylococcus bacteria on their skin and in their noses. They don't have staph infections. However, if that bacteria invades the mucosa and causes inflammation, redness, pain, etc., then the person is said to have a staph infection.

Hope that explains it somewhat!


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PostPosted: Thu Jan 28, 2010 2:34 am 
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Looks like the Chinese will need this natural immunity.

Another virus outbreak has closed this school. It just feels like H1N1 225 is about to explode.


http://www.news.gov.hk/en/category/heal ... n05006.htm


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PostPosted: Thu Jan 28, 2010 3:22 am 
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All I can add to clarify is that about 2 months ago I got a scratchy throat and an unusual cough that I had for a couple of days but that was it. I obviously can't say it was flu for sure but I have not had anything like a cough for years now since truly looking after myself (to an extent far more beyond the norm). I speculate this was H1N1 as it ran rampant at the same time through my school and something just felt different about this infection, albeit mild and not lab confirmed so just being honest. Again, I felt distinctly strange this time around in terms of symptoms but I say I was asymptomatic because it did not interfere with my daily routine and I did not take a day off work.

I have not had titers checked to confirm exposure but it must have occurred IMO. I am extremely healthy and in my 30's: relatively young. The risk of complications to this first wave, for me at least, seemed very small but the risk of vax complications slightly higher after doing some basic math: therefore, I choose natural immunity. With hindsight being 20/20 I'm glad I did with low reactor admission but no-one likes a Monday morning quarterback!

However, that was my choice and means nothing really to anyone else as we are all clearly very different.

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I post my opinions, they may or may not differ from accepted officialdom, but they ARE protected under free speech. Please consult your doctor (or your own mind) should you choose to take this information further.


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