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I hope I'm not boring *everybody* to death with this; I think infectious disease epidemiology is pretty cool. That's why I took that certificate program through UNC School of Public Health in field epidemiology (and I like being able to use what I learned!)
Yesterday, WHO raised the pandemic alert level to 5, out of a maximum of 6. OMG WE'RE ALL GONNA DIE! NO. Stop panicking. Here's what level 5 means: Phase 5 is characterized by human-to-human spread of the virus into at least two countries in one WHO region. While most countries will not be affected at this stage, the declaration of Phase 5 is a strong signal that a pandemic is imminent and that the time to finalize the organization, communication, and implementation of the planned mitigation measures is short.
To translate this: We've got a novel virus (never seen infecting humans before. See PSA #1 for why that's a problem.) It's been confirmed in more than one country. That's all.
It doesn't mean it's any "worse" than an average flu season, though the flu season in the northern hemisphere is just ending. It does mean, however, that there's *potential* for it to get worse, depending on what the virus does.
Remember in PSA #1 when I said RNA viruses are lossy? That means they mutate pretty easily. Some mutations may confer higher transmissibility and infectivity (fancy words that mean it's more contagious); others may confer higher virulence (which means it makes you sicker if you get it.) One thing we've learned from HIV is that some mutations that confer resistance to drugs make the virus weaker: there's a trade-off. AZT won't stop its replication anymore, but it's also not as good at infecting the host.
If a pathogen is *too* virulent, it will die out before it can infect too many people. If it makes a person so sick that they can't leave their house, it'll be confined to their house. (simplifying.)
The pathogen wants to strike a good balance between transmissibility and virulence. With viruses, you've got an incubation period where you're infected but not symptomatic (or only mildly), which means you can still pass on the virus before you know you're sick.
We *still* don't know why the Mexican cases were more severe. The only deaths have been reported in Mexico and in one 2-year-old who had been in Mexico recently. Is it because we've got better health care in the US and Europe? Is it because of poorer health and sanitary conditions in and near Mexico City?* Is it something different in the virus?
*It has been suggested that one of the reasons the Plague of 1340ish was so bad was because of the famine from about 20 years prior, so the kids didn't develop healthy immune systems. (The Great Mortality)
A couple paragraphs up, I mentioned that balance between transmission and virulence. If the virus traded off high virulence for increased transmission, it would be able to see more places. But remember that RNA viruses can mutate easily. There's a possibility that it'll mutate into something more lethal as time progresses.
The genomes from the Mexican cases have still not been released, but two isolates from cases presumably picked up in Mexico (from a NY tourist and a German tourist) are not very different from each other or from other published genomes, so the hypothesis that the difference is because of differences in the virus itself is less likely. (source)
Also, the man-bird-pig hybrid has basically been disproved. The lineage shows human and avian genetics several steps up the family tree, but the original strain was all porcine. (source) We can stop calling it swine flu, because it's basically mutated into a human virus.
UPDATE: Tara looks at the WHO scale, among other things, here.
Yesterday, WHO raised the pandemic alert level to 5, out of a maximum of 6. OMG WE'RE ALL GONNA DIE! NO. Stop panicking. Here's what level 5 means: Phase 5 is characterized by human-to-human spread of the virus into at least two countries in one WHO region. While most countries will not be affected at this stage, the declaration of Phase 5 is a strong signal that a pandemic is imminent and that the time to finalize the organization, communication, and implementation of the planned mitigation measures is short.
To translate this: We've got a novel virus (never seen infecting humans before. See PSA #1 for why that's a problem.) It's been confirmed in more than one country. That's all.
It doesn't mean it's any "worse" than an average flu season, though the flu season in the northern hemisphere is just ending. It does mean, however, that there's *potential* for it to get worse, depending on what the virus does.
Remember in PSA #1 when I said RNA viruses are lossy? That means they mutate pretty easily. Some mutations may confer higher transmissibility and infectivity (fancy words that mean it's more contagious); others may confer higher virulence (which means it makes you sicker if you get it.) One thing we've learned from HIV is that some mutations that confer resistance to drugs make the virus weaker: there's a trade-off. AZT won't stop its replication anymore, but it's also not as good at infecting the host.
If a pathogen is *too* virulent, it will die out before it can infect too many people. If it makes a person so sick that they can't leave their house, it'll be confined to their house. (simplifying.)
The pathogen wants to strike a good balance between transmissibility and virulence. With viruses, you've got an incubation period where you're infected but not symptomatic (or only mildly), which means you can still pass on the virus before you know you're sick.
We *still* don't know why the Mexican cases were more severe. The only deaths have been reported in Mexico and in one 2-year-old who had been in Mexico recently. Is it because we've got better health care in the US and Europe? Is it because of poorer health and sanitary conditions in and near Mexico City?* Is it something different in the virus?
*It has been suggested that one of the reasons the Plague of 1340ish was so bad was because of the famine from about 20 years prior, so the kids didn't develop healthy immune systems. (The Great Mortality)
A couple paragraphs up, I mentioned that balance between transmission and virulence. If the virus traded off high virulence for increased transmission, it would be able to see more places. But remember that RNA viruses can mutate easily. There's a possibility that it'll mutate into something more lethal as time progresses.
The genomes from the Mexican cases have still not been released, but two isolates from cases presumably picked up in Mexico (from a NY tourist and a German tourist) are not very different from each other or from other published genomes, so the hypothesis that the difference is because of differences in the virus itself is less likely. (source)
Also, the man-bird-pig hybrid has basically been disproved. The lineage shows human and avian genetics several steps up the family tree, but the original strain was all porcine. (source) We can stop calling it swine flu, because it's basically mutated into a human virus.
UPDATE: Tara looks at the WHO scale, among other things, here.
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no subject
Date: 2009-04-30 07:10 pm (UTC)From:There's pretty clearly a kind of geographic bias to the Federal one, which is natural to some extent i suppose. It seems to imply all disease start in other places, not North America, and then come over here. Clearly from a technical standpoint we should have skipped straight from level 0 to level 4, or possibly 5 depending on the definition of "throughout."
On the other hand, if one were to insist that you always have to hit stage X before you can go to stage X+1 then we could have the Great Green Plague start in the US and get 90% of the population wiped out and never make it up to level 1 because no one overseas has caught it yet ;)
no subject
Date: 2009-04-30 07:32 pm (UTC)From:I forgot to mention that the CDC has opened its emergency operations center and has initiated the distribution of the strategic national stockpile. What *that* means is that they're taking it seriously and using all resources to manage the crisis.
no subject
Date: 2009-04-30 07:11 pm (UTC)From:no subject
Date: 2009-04-30 07:32 pm (UTC)From:Somehow that depth of information utterly fails to make it in to the newpaper coverage, and while I hope the global severity is low, its stuff I wish I had time to research. (Also, it's interesting.)
Anyway, thanks for the summaries.
no subject
Date: 2009-04-30 07:40 pm (UTC)From:Newspaper and other general media coverage doesn't have time or space to be very deep, unfortunately. That's part of the reason most of my sources have been public health and science blogs, and the CDC's website. (And sometimes wikipedia, which is useful but still wikipedia. Which matches what I learned in school, mostly, so.)
no subject
Date: 2009-05-01 05:46 am (UTC)From:no subject
Date: 2009-04-30 07:45 pm (UTC)From:no subject
Date: 2009-04-30 07:46 pm (UTC)From:no subject
Date: 2009-05-01 03:07 am (UTC)From:I actually shared the definition of level 5 with a friend, to which I was greeted with "H1N1, Level 5, $50!" It's that insignificant. Still not to be trifled with... but yeah. This whole ordeal is less science and more manufactured hysteria.
no subject
Date: 2009-05-01 03:49 am (UTC)From:--Beth
no subject
Date: 2009-05-01 01:41 pm (UTC)From:Also, this post may help me figure out how to win at Pandemic. ;)
no subject
Date: 2009-05-01 02:07 pm (UTC)From: