Swine Flu: Why is it killing people in Mexico but not in the US?

[caseymoz]

I've noticed that overall, this flu has had a deathrate of 6% overall (horrible) but it seems to be killing people only in Mexico so far.

Anybody know why that would be?

I do have a guess: by far most deaths from the flu are caused by secondary pneumonia, which is typically an opportunistic bacterial infection that takes advantage of the flu victim's exhausted immune system. This bacteria usually isn't strong enough to stand against a healthy immune system, though.

So, maybe the difference is in the bacteria?

In the US, we do have some pretty nasty multi-resistant bacterial strains, but those will harm or kill people even beginning with a fairly healthy immune system. Maybe a usually-benign form of bacteria that's common in Mexico isn't nearly as common in the US?

Another conjecture: Maybe our, often disparaged, use of antibacterial soaps has actually helped us out here?

It would go to show how a small change in a peoples' habits could lead to a very big change in outcome.

[Mojorabbit]

1. I think that may be part of it

The docs on the listserv for emerging infectious disease physicians are speculating it is a testing bias, Mexico is testing hospitalized patients and we are testing outpatient. If so it will even out soon enough.

It is also possible that there is a slight mutation of the Mexico strain that is occurring here. I guess we will know in a couple of weeks.

[targetpractice]

2. It's not bacterial pneumonia

The secondary pneumonia is due to fluid leaking into the lungs because of an uncontrolled immune response to the H1N1 virus. An overly-aggressive immune response in healthy people can cause "cytokine storm" resulting in damage to the lung tissue.

You can read more about it here... http://en.wikipedia.org/wiki/Cytokine_storm

Unfortunately, the robust immune systems of 20-40 year olds may be a liability. This may explain why young adults are showing up in Mexico City hospitals. Mexican children may be experiencing mild cases (like in the US) and are not reporting to the hospitals... therefore they are not being counted. Most of the US cases are in children.

[caseymoz]

7. You're mistaken. Cytokine storm is one form of pneumonia that causes flu fatality

The most common pneumonia related deaths with influenza are bacterial:

http://www.cdc.gov/EID/content/14/8/1187.htm

http://www.sciencedaily.com/releases/2009/03/090317111904.htm

However, medical records indicate the Spanish Flu commonly induced cytokine storm. As you've pointed out, that's probably a vulnerability for 20 to 40 year-olds, and it could be a reason why that flu killed in all age groups. Doctors during the Spanish Flu described puzzling symptoms in patients, which hampered diagnosing the disease in the early outbreak. It was Cytokine Storm.

I don't have the link yet, but I did read that testing of exhumed remains from victims of the Spanish Flu indicate that mortality due to bacterial pneumonia was still a strong factor.

[targetpractice]

10. Ummm... According to your CDC source....

... Bacterial co-infections are only found within 25% of pneumonia-related influenza deaths.

Therefore, it is wrong to say "The most common pneumonia related deaths with influenza are bacterial."

[caseymoz]

11. I'm so sorry. You're right!

Put me in the corner.

:dunce:

I saw it I thought in this source, apparently I remembered wrong, and probably misinterpreted the stat. Too rushed and not enough sleep. :dunce: :dunce:

I'm moving. I'll be back next week, and I hope this thing is somehow under control then.

[kestrel91316]

3. Well, for one thing, they have about 2000 cases at last count, and we

have 40.

[caseymoz]

8. That is a small sample.

But I would still think we'd see one.

Of course, we're reporting mostly outpatient. It could be that people had died in the US before the disease was noticed here.

[Warpy]

4. We've only seen a handful of cases in the US

It seems pretty clear that Mexico is getting the worst of this one so far and that what's being reported are only their worst cases.

We haven't seen the severe cases yet because we haven't had enough of them yet.

[Sebass1271]

5. I've also read in a bloomberg article that in 1976

the U.S. encountered this same type of flu..however, it was mandatory by the health organization to get vaccinated to prevent future outbrake... this could also be one of the reasons.

[Why Syzygy]

6. But, only about 25%

of the population was vaccinated before they canceled it due to the illness and deaths from the vaccine. I don't even remember it. I'm sure I didn't receive a vaccine.

[MercutioATC]

9. NOT "this same type of flu".

Yes, it was a swine flu. 40M Americans got vaccinations. Because it was a type A vaccine, it may provide a slight mitigating effect, but this is a completely different strain and the 1976 shots do NOT immunize for this strain.

[tiptoe]

12. Ozone pollution in Mexico City is "severe" == UVB being absorbed = Vitamin D synthesis blocked. See:

Notice what Los Angeles has in common with Mexico City (and click the news link):

http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=389x5558402#5558640