Who dies in a flu pandemic?

April 27, 2009 7:37 AM

In a flu pandemic what determines who dies?

I've been researching this a little but cannot seem to find an answer. I've been wondering if it is possible to pre-identify who will die in a flu pandemic. I understand that the very young, very old and those with compromised immune systems are at greatest risk for dieing in general but what determines who else dies? I had always assumed if you were really healthy then you would be able to fight it off. But, in reading about the 1918 influenza it seems that most of the victims were "healthy young adults". Why would this be?

posted by tr45vbyt to health & fitness (14 comments total)

Check out this recent comment. Most notably:

"The leading theory on why so many young, healthy people die in pandemics is the “cytokine storm,” in which vigorous immune systems pour out antibodies to attack the new virus. That can inflame lung cells until they leak fluid, which can overwhelm the lungs, Dr. Moscona said.

But older people who have had the flu repeatedly in their lives may have some antibodies that provide cross-protection to the new strain, she said. And immune responses among the aged are not as vigorous."
posted by inigo2 at 7:39 AM on April 27

Coincidentally, I wrote a news blurb on this quite recently!

In the interest of not-self-linking, let me give you the highlight of the paper I wrote about :
Moderating influenza's immune response

The extremely simplified theory: There is a noted difference of who dies due to seasonal flu strains versus the highly-pathogenic pandemic and epidemic-level flu strains. Since the highly pathogenic strains kill the young and healthy, one theory is that it is precisely the healthy individual's robust immune responses which leads to respiratory injury and death.
posted by NikitaNikita at 7:48 AM on April 27

So would it be possible to save the healthy people by giving them drugs to kick their immune systems down a notch? That's how they usually treat autoimmune diseases. Or would that just make them vulnerable to dying from the primary flu infection?
posted by craichead at 7:52 AM on April 27

In the pandemic of 1918, you also had young men at war living/fighting/recuperating in close proximity, so the flu spread quickly through "healthy" populations that way. But I think that in general, some flu strains affect the young and healthy for reasons attributable to the reasons inigo2 discusses above. The cytokine storm is a killer - that's why you should get drunk and keep your immune system suppressed until this thing has blown over! (just kidding, obviously)

Also, has anyone else noticed a lot of people spelling dying as "dieing" lately? Any idea what's up with that? I swear I've read that exact spelling in at least three different places lately, and have never seen it spelled that way before.
posted by billysumday at 7:57 AM on April 27 [2 favorites]

Check out this graph, which shows age vs fatality for different pandemics.
posted by Mike1024 at 7:58 AM on April 27

In the 1918 pandemic most people died as a result of the pneumonia that often accompanied the flu virus. There were no antibiotics in 1918.
posted by Gungho at 8:00 AM on April 27

There were no antibiotics in 1918.

That's true, but irrelevant. Flu is a virus, so you need antivirals, not antibiotics.
posted by craichead at 8:10 AM on April 27

The issue of no-antibiotics is related to pneumonia -- it's a frequent secondary-infection in those who have a bad bout on the flu. Thus, pre-antibiotics, you might survive the flu to then get pneumonia afterwards which turned out to be fatal.

There has been some interesting research about the 1918 flu, which seemed to show that the virus itself was more harmful to cells than other strains of flu. Even within the "influenza A" category of virus, there is variability in how outright damaging or lethal the virus is to individual cells.

As someone else pointed out, cytokine storms can be an issue as well, and there are probably individuals more prone to cytokine storms than others. That being said, the virus itself may also have differing ability to trigger a cytokine storm, such that if the 1918 virus more readily caused it than other strains (which is a reasonable possibility given that it was more directly lethal to cells), it could kill a greater proportion of young healthy individuals.
posted by davidnc at 8:28 AM on April 27

I don't think that's what happened in the 1918 epidemic, though, davidnc, because it wouldn't explain the distinctive pattern of deaths in which young, healthy people were more likely to die than old people or the very young. It makes more sense for it to have been cytokine storm, rather than opportunistic pneumonia, because opportunistic pneumonia would be more likely to kill those with weaker immune systems to start out with.

According to wikipedia, doctors have tried to used corticosteroids to fight off cytokine storm, but it doesn't seem to work. So my idea was not crazy but was still wrong.
posted by craichead at 8:40 AM on April 27

There were no antibiotics in 1918.

That's true, but irrelevant. Flu is a virus, so you need antivirals, not antibiotics.

Yes, but Pneumonia is not a virus. RTP. Also then like now people were asked to wear masks which were/are inefficient at filtering out viruses. But if you're hacking up a lung it is probably better than nothing.
posted by Gungho at 8:48 AM on April 27

Yes, but Pneumonia is not a virus.

I'm not a doctor, so I don't know what I'm talking about. But I thought pneumonia was a condition that could be caused by bacteria, a virus, or something else. If it's caused by bacteria, antibiotics will work on it. If it's caused by something else, they won't.

Also then like now people were asked to wear masks which were/are inefficient at filtering out viruses. But if you're hacking up a lung it is probably better than nothing.

Better than nothing, and also it makes people feel better to be able to do something, anything.
posted by craichead at 9:17 AM on April 27

In the last decade I heard about some research suggesting that a large part of the 1918 pandemic's fatality rate was that it took out most of the large number of people who already had tuberculosis. Has this been largely dismissed?
posted by kimota at 9:25 AM on April 27

Actually, "pneumonia" is a term that describes a condition, not a cause. "Hepatitis" is another word like that; it means "liver disease" without specifying what causes it. (Hep A is a virus. Hepatitis can also be caused by toxins from mushrooms, and by toxoplasma protozoan.)

Pneumonia can be caused by viruses, by bacteria, or by chemical irritants. One of the ways that mustard gas can kill is by causing pneumonia.
posted by Chocolate Pickle at 1:01 PM on April 27

I just wanted to add that while various sources have been postulating that this flu might also be killing the young and healthy in disproportionate numbers due to causing a "cytokine storm." First, the US cases have been pretty mild, including those high school students in NY. Also I haven't found good numbers on actual death rate of those infected. Yes, it seems to be the case that a good number of the Mexican fatalities have been young adults, but we don't know how that relates to the ages of the infected population. I wouldn't be surprised if more of the infected were young adults because I'd expect them to be more social and mobile.
posted by Good Brain at 2:04 PM on April 27