Swine flu and the Mexico mystery


"Swine Flu and the Mexico Mystery," my story on the swine-flu outbreak, is up at Slate. It looks at a question hotly pursued right now: Why does this flu seem to take a much deadlier course in Mexico than elsewhere so far? The answers will suggest much about what's to come.

Of the two two qualities vital to a nasty pandemicm-- to spread readily, and to be deadly, -- this flu,a brand-new strain of swine flu, or H1N1, seems to possess the first: Evidence is high that it spreads readily among humans. In that sense, it's an inversion of the bird flu. Bird flu terrifies infectious disease experts because it kills about half the humans that get it--but it has so far failed to develop the ability to jump easily from person to person.

This swine flu, meanwhile, does seem to spread easily by airborne transmission. But how deadly is it? Despite the 100+ deaths in Mexico, we don't really know. And that's is why epidemiologists are working frantically to figure out the Mexico mystery: Why do the death rates there appear to be so much higher than those in the United States? In Mexico, it has reportedly killed about 100 of the 1,600 official suspected cases; elsewhere, it has appeared to take a far milder course, with zero deaths out of the approximately 300 instances. There are several possible explanations for this discrepancy--any one, two, all, or none of these ideas could shed light on how deadly this virus might prove.

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Two additional possibilities

1. More than half of the Mexican
population have no medical insurance.
Hence, unless they have one foot on
the grave, they do not seek medical
help. In this case, that makes the
illness worse.

2. Mexicans have far less frequent
general flu than the Americans (because
of less air conditioning) hence Americans
are more resistent to the virulent version.

Tapen Sinha
ING Chair Professor of Risk Management
ITAM, Mexico

Hence, unless they have one foot on
the grave, they do not seek medical
help. In this case, that makes the
illness worse.

In that case, it makes the illness seem worse; the 2000 reported cases could easily be 200,000 unreported cases, with folks at home in bed with fairly mild symptoms.

Ratios of random numbers are very sensitive to small wobbles; in this case, we may have huge wobbles, making the death ratio completely indeterminate. We will have to wait and see until we have some better way to narrow down the data, since we have a data set that can not be analyzed parametrically, compounded by unknown distributions for our sampling in the first place.

Due to the nature of the 1918 influenza that epidemic was deadlier to healthy young adults 25-45 than other population groups. If the new swine flu is similar to the 1918 then the age distribution differences between the US and Mexican population could account for some of the difference, i.e., we are on average older than Mexico.

There's a 4th (or 5th or 6th or 7th) alternative, which is that this is a slightly more severe strain of flu than what's typically seen, but it's * STILL * JUST * THE * FLU.

Remember how poor Gerald Ford allowed the experts to panic him into practically ordering the whole country vaccinated against swine flu back in 1976 and instead of saving us from the flu the vaccine created a mini-epidemic of Guillane-Barre syndrome? I'm starting to think that this is a gross overreaction as well.

Just look at the numbers: While the MSM are breathlessly reporting that: (a) about 100-110 people have died, all victims in the healthy age cohort of 25-50, (b) of 1,324 identified cases 929 have been treated and released from the hospital, and (c) nearly 2,000 people in Mexico have been hospitalized with serious cases of pneumonia since the first case of swine flu was reported two weeks ago, you almost NEVER see the answer to the question begging to be asked: how many of these things does Mexico have in a NORMAL year? For gosh sakes, they've got about 110 million people, with 20-25 million crunched into greater Mexico City alone.

Shall we run the math? Due to the fact that Mexican data is hardly available, my best angle of approach was to use US data and then divide by 3 since the US population is roughly 3x that of Mexico. So.
If the US has a population of 300+ million and 36,000 flu related deaths per year (according to the CDC), then with a population of 110 million Mexico probably has about 12,000 flu deaths per year or 1,0000 per month IN A NORMAL YEAR.

So trying to tease out rough numbers in a fast moving Swine Flu situation, Mexico is officially counting 103 deaths (let's use a timeframe of a month) with roughly 1,324 patients hospitalized and 929 of those treated and released already.

In a typical month historically, Mexico probably has about 1,000 deaths from the flu and while the majority of those patients are probably outside of the ages of 25-50, not all of them are . . . . if just 10% of the flu related deaths in a typical year in Mexico are in the 25-50 age bracket, that's 100 flu related deaths per month aged 25-50. Hmmmm.

So, I'm starting to have a hard time seeing this flu in its current incarnation (which I think I had and recovered from with no problems, though Relenza gets a H/T after the 2nd day) as anything more than a unique strain of Type A H1N1, suggesting that any prior flu vaccinations and natural exposures provided little or no protection and so this flu kicks like a country mule, as they say back home, but doesn't do any more lasting damage than THAT.

Noodling the data further, according to the NCHS and CDC, the U.S. had approx. 1.3 million hospitalizations due to pneumonia in the US 2002 (2001 National Hospital Discharge Survey, NCHS, CDC). The U.S. population is older than Mexico's and so our pneumonia patients probably have a hospitalization rate that's higher than theirs, so let's use 1.3 mil./300 mil. and multiply by the Mexico population of 110 million * 0.5 -- conservatively guessing that their hospitalization rate for pneumonia is half that of the U.S. due to younger age. That gives an annual estimate of pneumonia patients in Mexico hospitalized of about 240,000 people. So the monthly rate in a typical year could be around 20,000 per month or maybe 10,000 per half month. [Note: some observers suggest that flu and pneumonia complications in a normal flu year could be higher than that due to the smog in Mexico City, but in the interest of conservatism let's ignore that].

Why exactly are we supposed to be surprised that there are reportedly nearly 2,000 people in Mexico hospitalized with severe pneumonia over the past two weeks, when that number (if accurate) is measurably lower than typical experience. It's a country of 110 million people, after all.

Sometimes the total cluelessness of the MSM makes my teeth hurt . . . . . . or maybe this is the worst thing to hit Mexico since Cortes marched through, but you can't make that claim AND believe that the numbers in the media reports have a shred of credibility, either.

You'll want to fix your own "bad math":

"about 100 deathsâsuggesting a mortality rate of 6 percent. This is almost certainly bad math, as the total case count almost certainly ignores thousands or tens of thousands of other cases that have taken milder courses like those in the United States. It's perfectly conceivable Mexico has actually had 10,000 or 100,000 casesâor even 1 million cases. If so, then the kill rate would be not 6 percent but 0.1 percent (given 10,000 cases) or 0.01 percent (given 100,000 cases). If it's 1 million cases (quite possible if this thing really spreads easily) then the mortality rate is just 1 in 10,000."

You're off by a factor of ten. If there were 10,000 cases, then 100 deaths makes 1.0 percent, not 0.1 percent. Similarly, if there were 100,000 cases, then one in a thousand or 0.1 percent (not 0.01) would have resulted in deaths. You are right that if there were a million cases, the mortality rate would be one in 10,000 -- but that is 0.01 percent.

By johnshade (not verified) on 28 Apr 2009 #permalink

You're clearly right about the gross underestimate of infections in Mexico. Here in New Zealand a school party of 25 went there for three weeks, 11 of them came back with Swine Flu. However you look at it that makes the virus far more infectious than the official count of 1300 infections.

What I find interesting is that no cases have been reported in Asia yet. It's unbelievable that it hasn't reached there. If there is any significant danger in this pandemic it could well emerge from there. Large populations living in close proximity with livestock, unsanitary conditions and poor healthcare. I think we've got a few nasty surprises yet to come.

The US & Mexican Government (in conjunction with one another) are over-exposing this whole thing for the purpose of keeping people away from Mexico. Between the fact that Mexico has always been a huge hotbed of UFO and Government activity (and experiments) and the reason finding of a mysterious creature (DNA shows as nothing we know of thus far), it's no wonder that they are suddenly quarantining much of the Country by faking some huge outbreak. They need people to stay home and clear of what project thy need to complete.