Can You Get H1N1 More Than Once?

[Flufreak]

Re: Can You Get H1N1 More Than Once?

I haven't read that severe symptoms should be required.
AFAIK, asymptomatic should work fine.

And protection is never 100%, 90% is very good

I agree totally that many people have been tested and show immunity and can not remember illness. I would be very interested to see a study that shows how many confirmed cases do not have immunity when tested later.

 

[North44]

Re: Can You Get H1N1 More Than Once?

I haven't read that severe symptoms should be required.
AFAIK, asymptomatic should work fine.

And protection is never 100%, 90% is very good

It has always been my understanding that, in healthy individuals, the more virulent the infecting organism or infection, the greater the immune response (with corresponding antibody titres). I know you like hard evidence, but I don't have a study readily available at the moment. When I find one, I will pass it along.

 

[gsgs]

Re: Can You Get H1N1 More Than Once?

I could understand that for T-cell immunity, where the virus
must come to the cell in question, so it can be protected.

But not for humoral (B-cell), when it's in the blood,
no severety required here.


?

 

[North44]

Re: Can You Get H1N1 More Than Once?

I could understand that for T-cell immunity, where the virus
must come to the cell in question, so it can be protected.

But not for humoral (B-cell), when it's in the blood,
no severety required here.

On further reflection, I suspect you are correct. I have confused humoral and cell-mediated immune response. If I remember correctly, there was a concern about individuals being treated with acyclovir in early chickenpox and whether they formed antibodies, despite a milder infection. The evidence is yes, they do mount an appropriate antibody response.

 

[blacknail]

Re: Can You Get H1N1 More Than Once?

I haven't seen much from Niman lately, but he recently posted some comments on this topic:

Weak Immune Response In Mild Cases Driving Re-Infections? (10/10/09 16:02)

Buffalo School Outbreaks Raise H1N1 Re-Infection Concerns (10/08/01 12:45)

I'm not sure if I can copy this here, but essentially there seem to be a lot of reinfections in patients who did not have fevers with their initial bout. Not much info on the severity of the subsequent infection.

 

[pjie2]

Re: Can You Get H1N1 More Than Once?

I'm not sure if I can copy this here, but essentially there seem to be a lot of reinfections in patients who did not have fevers with their initial bout. Not much info on the severity of the subsequent infection.

Are they proven to have had swine origin H1N1 the first time round? I can't believe there were many doctors sending off samples for testing from patients with no fever. I guess if they had confirmed influenza A in the off-season, you can assume it was H1N1, but again, how many doctors were running the flu tests on patients without a fever?

I'd lay at least a moderate sum of money that there's a lot of people who had some random feverless cough or cold over the summer, decided they had H1N1 and are now once again self-diagnosing a second infection. That is, this particular observation has more to do with man-flu than swine flu.

 

[tropical]

Re: Can You Get H1N1 More Than Once?

#126: "cold over the summer" .. "man flu"


When the budget/insurances payed institutions are pretty vaccant with tests conductions,
and when many GP's follow the non-tests-if-not-temp/hospitalized mantra,
displacing generic "flu-like" / "viroses" / "atypical" diagnoses mambo,
the many affected folks are pushed to be half-self-made doctors, to asses their individual recurrent or out-of-season symptoms into a context of an WHO declared worldwide pandemic stage maximum phase (6).

Now, every senior human without persistant chronic respiratory illness,
when having a summer cold,
could pretty well feel the diference from an actual strange summer illness with heavy cough / laringo-throat / synus/ear inflamations
(all that sometimes with medium-high temp.),
which seems to be an pretty ordinary symptoms pattern for this pandemic flu wave,
compared to few coughs / sneezes / leaking nose, ordinary summer cold symptoms.

Or maybe we must act as this pandemic does not exist at all ...

to not ruin its worldwide "perfect handling" picture ...

 

[North44]

Re: Can You Get H1N1 More Than Once?

Are they proven to have had swine origin H1N1 the first time round? I can't believe there were many doctors sending off samples for testing from patients with no fever. I guess if they had confirmed influenza A in the off-season, you can assume it was H1N1, but again, how many doctors were running the flu tests on patients without a fever?

I'd lay at least a moderate sum of money that there's a lot of people who had some random feverless cough or cold over the summer, decided they had H1N1 and are now once again self-diagnosing a second infection. That is, this particular observation has more to do with man-flu than swine flu.

I agree. It is all very nebulous. People talking as if it is fact. I have yet to see any proof of second infection (documented).

 

[gsgs]

Re: Can You Get H1N1 More Than Once?

they are withholding it

Anne Schuchat doesn't epect NYC to be protected from wave 1

they looked at 50 cities and found no protection wave1-->wave2

 

[Mamabird]

Re: Can You Get H1N1 More Than Once?

they are withholding it

Anne Schuchat doesn't epect NYC to be protected from wave 1

they looked at 50 cities and found no protection wave1-->wave2

I believe that the Doctor's point was that since only about 10% of New Yorkers (and others in the remaining states) were likely infected during the first wave, that there was still a target rich environment for the virus in a subsequent wave until the population could be vaccinated. I have not seen or heard anyone from CDC indicate that a person infected with Swine Flu in wave one, has little immunity in wave two or three. So I believe that they are speaking of the population as a whole, not individuals.

 

[gsgs]

Re: Can You Get H1N1 More Than Once?

why does the wave go down ?
Because they acquired herd-immunity.

How long does it last ?
At least 2 months, see the intervals between waves.

Can a vaccine be better than that ?
Natural infection should be superior

10% seems to be enough, if the superspreaders are immune

I've seen estimates recently that including asymptomatic cases,
20%-40% had been infected in NYC

 

[North44]

Re: Can You Get H1N1 More Than Once?

"Herd immunity describes a type of immunity that occurs when the vaccination of a portion of the population (or herd) provides protection to unprotected individuals. Herd immunity theory proposes that, in diseases passed from person-to-person, it is more difficult to maintain a chain of infection when large numbers of a population are immune."

Why would herd immunity "last for 2 months". If there are 2 month waves, it is not because people lose their immunity but rather because the prevalence of the virus itself fluctuates for various reasons.

Although in theory illness may be superior to vaccination in creating protective immunity, widespread vaccination has managed to reduce or eliminate many illnesses over the decades. It has been very effective in protecting vulnerable populations from influenza

There is no data to suggest 20% - 40% of the population has immunity. It is all speculation; not based on fact.

 

[gsgs]

Re: Can You Get H1N1 More Than Once?

***** ignores New York City (and London). Why are they spared ?
Was these schools in Buffalo also hit in wave 1 ?
CDC should show their data from those 50 cities, so it can be
checked and discussed.

 

[gsgs]

Re: Can You Get H1N1 More Than Once?

the 20-40% are from this thread:
http://www.flutrackers.com/forum/showthread.php?t=127659

> New York City health officials now believe that while only 10 to 20 percent of New Yorkers
> were reported ill with flu last spring, as many as 20 to 40 percent may have been exposed
> to the disease and developed immunity that has prevented it from spreading.

some health officials ? most health officials ?
Is it all just speculation ?

they could do some serology - and maybe did.
they could have done some more questioning of the people to find
out who had had it - and probably did.

They may well have more information than we.

It sounded a bit as if they had come up with the 20-40% because
they thought that so many were needed to explain the herd immunity
why NYC is spared now.
That would be hard to explain with only 10% being infected,immune.
Remove those 10% and we have a city with 7.5M instead of 8.3M,
a little less densely populated, but why should those remaining
90% be less vulnerable to the virus than some other city
with 7.5M ? Being less densely populated doesn't usually protect cities
from flu.
But we know from seasonal flu that these 10% are indeed
sufficient to provide herd-immunity since seasonal waves
end. They go down when only ~10% of the population are infected.

So, why does herd immunity occur ? I assume it's because the
superspreaders are no longer dangerous because of immunity.
The average number of flu-critical contacts is going down.
That would mean, flu-sufferers are more often superspreaders
than other people
Remove these 10% of superspreaders from a city and they should be safe. (?)

Well, removing immune people also increases the contacts between susceptible
people .
And we have the modelings which apparantly can explain this all.

I'm confused...

 

[gsgs]

Re: Can You Get H1N1 More Than Once?

> Resurgence in areas hit hard previously are not an indication
> of reinfection, but rather new infections among the population
> that were spared previously (and don't have immunity).

why were they spared previously while living through a whole wave
but not now when they just only help to build a new wave themselves ?

 

[silvergirl]

Re: Can You Get H1N1 More Than Once?

Maybe it is because they closed some of the schools in the spring -in NY etc...heading off widespread flu?

 

[blacknail]

Re: Can You Get H1N1 More Than Once?

Regarding herd immunity, if the R0 (attack rate) is below a certain number (say 1) then the virus will die out because less than 1 person is infected by each case. Let's say the R0 is 1.2 for this virus. If 25% of the population is immune then the R0 drops below 1 and the virus dies out. Now if after 2 months that immunity level drops to 10% of the population and you have more infections.

 

[gsgs]

Re: Can You Get H1N1 More Than Once?

> Let's say the R0 is 1.2 for this virus. If 25% of the population is
> immune then the R0 drops below 1 and the virus dies out.

hmm, yes. Everyone has a certain number of contacts, independent
of whether those had been infected before or not.

If you are infectious then each of these contacts is infected with
probability R0/C , where C is the number of contacts. (simplified)
For those who are immune, this probability sinks. So the overall R0
sinks to.

When we just remove the immune people from the community,
then you would seek other contacts in compensation for the lost ones.

So, if everyone reduced his contacts by 25%, that should be just as
good as having gained immunity for 25% of the people in the community

Alternatively add immune persons to a community to increase
its herd-immunity - just because people build new contacts
to those and in compensation give up contacts to other
community members.

(?)

 

[North44]

Re: Can You Get H1N1 More Than Once?

> Resurgence in areas hit hard previously are not an indication
> of reinfection, but rather new infections among the population
> that were spared previously (and don't have immunity).

why were they spared previously while living through a whole wave
but not now when they just only help to build a new wave themselves ?

A portion of the population is affected by each wave. Who and how many are determined by:
-virulence of the virus
-environmental/living conditions
-health of the individual/population
-degree of exposure (contact with others)
-luck

 

[Flufreak]

Re: Can You Get H1N1 More Than Once?

A portion of the population is affected by each wave. Who and how many are determined by:
-virulence of the virus
-environmental/living conditions
-health of the individual/population (immune status percentage and degree)
-degree of exposure (contact with others)
-luck

- transmissibility of the virus


I would recommend adding (in red)