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Swine Flu: Clearing Up The Numbers
As we try to figure out just how concerned to be about swine flu (yeah, we're still calling it that, even if Obama won't), the key indicator we're all looking at is the scale of the outbreak in Mexico, where all this appears to have begun (though that's no longer certain (sub. req.)).
But the Mexican government has used several different metrics to gauge that question. And the numbers, of course, have been been constantly shifting in the last few days as the situation changes. So we thought we'd try to clear up the confusion by briefly laying out what the different numbers are, and what they mean.
Suspected Deaths
One metric that the Mexican government has used is suspected deaths. But it's not clear what evidentiary threshold they're insisting upon to declare that a death was probably caused by swine flu. Indeed, the government appears to have shifted on that point, perhaps under pressure from foreign an international health organizations.
On Tuesday, the Mexican government announced that the number of suspected deaths from swine flu was 159, up only slightly from 152 on Monday.
Then on Wednesday, Health Minister Jose Cordova reduced the figure to 84, saying that tests had shown that swine flu wasn't the cause of many of almost half of the 159. Yesterday, according to a transcript provided by a reporter, Cordova went before the cameras again, and stuck with the 84 figure, saying explicitly that the WHO and CDC had been working with Mexico to get those numbers.
But he also announced that the government would no longer provide figures for suspected deaths. Reading between the lines, it looks like, under pressure from outside health organizations, the Mexican government was forced to accept that its "suspected deaths" numbers weren't reliable.
Confirmed Deaths
The government has also been giving out the number of deaths that have been scientifically confirmed to have been caused by swine flu. On Wednesday, Cordova had put that number at 8. He updated it yesterday to 12, and this morning, the government raised it to 15, based on lab tests, while saying the virus was "not so aggressive" as initially feared.
Confirmed Cases
This is the number of Mexicans who have been confirmed to have swine flu, including the confirmed deaths. Earlier this week, the government put that number at 49. On Wednesday, the Mexican president, Felipe Calderon, said it had risen to 99. Yesterday, Cordova again raised it to 260, and this morning to 328.
So the "confirmed deaths" and "confirmed cases" numbers seem to be the best thing to focus on. It's looking like many people who are getting the virus are recovering, so the deaths number may be more relevant -- but no one knows whether that trend will continue.
Josh
Zachary
Let's compromise. How about pig flu?
May 1, 2009 10:31 AM | Reply | Permalink
Let's really get the pork lobby into a tizzy and start calling it "porcine death". Or maybe "bu-baconic plague"?
On the one hand, nobody had a problem with "avian flu". On the other, I was really curious as to why the Texas governor wanted to give Tamiflu to pigs.
For me though, as inconsequential as the name of this crisis seems to be (a head cold by any other name?) it really bothers me to see the government (and the WHO for christ's sake) succumbing to the marketing desires of corporate lobbies. It seems like the hog industry could be doing all sorts of valuable things in this situation - providing information about the outbreak including a disclaimer about pork products being safe, providing testing of workers and observing livestock for signs of illness, providing support to responding organizations, etc. Instead they resort to influence peddling.
Maybe what Brownie really should have done when Katrina made landfall was to hire a really good PR firm.
May 1, 2009 6:24 PM | Reply | Permalink
Pigs fly?
May 3, 2009 3:00 AM | Reply | Permalink
The Obama has taken a political approach to the possibility of a swine flu pandemic.
They are taking a win-win approach politically.
There are two possibilities:
There could be a pandemic. In that case they have warned the people of the USA ahead of time.
or, there may not be a pandemic. In that case the warnings by the Obama Administration served to prevent any pandemic.
The only way to lose politically would be to not inform and warn the American people and there was a pandemic. In that case they would have abrogated their responsibility to keep America safe.
.
May 1, 2009 10:49 AM | Reply | Permalink
The Obama?
Anyway, how so? It seems like he is listening to health experts and following their advice.
I don't see it as political.
May 1, 2009 11:14 AM | Reply | Permalink
The Mexican Government seems as suited to disease control as it is to fighting drug cartels. I have a feeling the majority of those previously announced "suspected cases" either weren't tested at all for the new swine flu or weren't tested correctly - aka not enough cells in the sample.
If you read the AP piece of Mexico's initial response and subsequent followup it will not give you any confidence in having them at the forefront of this thing. They have consistently lied to patients and dropped the ball when it comes to tracking the path of infection and treating those who are ill.
I honestly don't think you can trust any information coming from south of the border and that we are gonna find out just how serious and fatal this disease is through our own experiences in the US.
May 1, 2009 11:25 AM | Reply | Permalink
I don't mean to say that this strain is highly fatal etc , just that we aren't gonna know what we're dealing with til it runs its course further in the US.
May 1, 2009 1:21 PM | Reply | Permalink
I think the Swine Flu IS a big deal. Even if it is no more deadly than Regular Flu, it is ADDITIONAL. If Swine Flu is to be ranked by whether or not it kills more people in the US yearly than REGULAR Flu (let's say 35,000)....Are we to get into a tally race where Reg Flu kills 35,000 and Swine Flu kills 34,000 and we say AWWW, whats the big deal with Swine Flu it is no worse than Reg Flu?
And there is no question, our human numbers and pressure-cooker incubation methods of raising animals (injecting and feeding them all the while with massive doses of antibiotics and hormones) is just BEGGING for trouble. I am fascinated and horrified by human's capabilities to do the STUPIDEST things in pursuit of money. And these people are persuaded into thinking they are doing the SMARTEST thing, because of their soul destroying worship of money - as if it were a physical law. As if doing the smart thing, in the short term, for money was blessed by the universe and in harmony with the spheres.
We have the capabilities of thinking LONGER TERM than any other species we know of. Yet, we appear doomed to think and act without any regard for our future. A fruitfly has a better set of ethics and long-term goals.
May 1, 2009 11:27 AM | Reply | Permalink
We've also been feeding anti-viral drugs to animals to keep them from getting flu.
May 1, 2009 4:12 PM | Reply | Permalink
The deal with this is that it hasn't grown to epic proportions, death toll wise, yet and really it doesn't seem to be heading that way anytime soon. The fact that it is receiving so much media coverage is annoying because it isn't even close to a pandemic or epidemic yet. There's really no need to panic yet but all the media coverage is making people freak out. More on this here, http://www.newsy.com/videos/swine_flu_precaution_or_paranoia/
May 4, 2009 1:05 PM | Reply | Permalink
The key metric that has led to the likely erroneous conclusion that Mexico's outbreak is more lethal than ours is the ratio of confirmed deaths:confirmed cases. For reasons discussed in this post, the Mexican ratio's numerator and denominator exhibit significant ascertainment bias. OTOH the bright spotlight the US media have shone on the piggy flu probably means that all deaths and the majority of cases have been detected. Before we draw any conclusions about the likelihood of piggy flu-associated deaths we need apples to apples comparisons.
May 1, 2009 12:31 PM | Reply | Permalink
ptboya is correct. Mexico has no idea how many cases of flu they are dealing with. As for the deaths, it is always the same. Medical practitioners always look for another cause of death to supress the statistics even if the cause is a result of the primary problem. This is particlarly true in drug testing when they blame everything except the drug, because it was the doctor that prescribed the drug.
May 1, 2009 12:56 PM | Reply | Permalink
Frustrating as it is to everyone, when we are relying on another country for data, we are also stuck with their criteria until forensic research is completed. Some may think that Mexico may not be as scientifically sophisticated as the US, but they used whatever technology they had available. Only an after the fact review will they learn how to handle a suspected outbreak better. Personally, I would have them err on the side of caution than to have a new communicable virus out and not have the countries reporting on it for fear of retribution / ridicule. Though having the President of any nation being the talking head on a daily basis may be a little over the top.
The silver lining: (2) - this was a test of our system to respond to a health emergency and it highlighted our need to have a full staff of trained professional at all our public health facilities.
May 1, 2009 2:27 PM | Reply | Permalink
This is a big deal.
It's an influenza virus with a new genetic configuration. It's a strain which has never been seen before. It's a new variant infecting humans -- and no one knows what that new genetic makeup means for the virus' transmissiblity, or lethality.
Proof of human-to-human transmission is one red flag; another is how easy the transmission is. Multiple, global outbreaks with numbers of confirmed infected ramping up quickly means it's a new virus that can spread quickly from person-to-person, and against which humans have no real immunity. If the confirmed Case Fatality Rate numbers also increase -- well, then we're screwed.
Viruses mutate as they're transmitted through a population, as their genetic material recombines. This process is a Darwinian crapshoot, but it means the virus is "trying" different combinations -- and the version of the virus that can incubate quickly, spread easily, and not kill its host (or, not too fast) means that particular strain will become dominant, even established in another host (pigs, fowl) to be re-introduced into the human population later.
No one knows what that process will do with this virus. There is some data suggesting that the 1918 version of H1N1 arrived as a mild but fairly transmissible virus, then recombined with other genetic material and re-emerged several month later as a real killer.
The 1918 'Spanish Flu' Pandemic -- and observed patterns of "behavior" in flu and respiratory disease outbreaks since -- are the template around which virologists and health organizations have created their response plans, shaped 1918-19 in the same way that government responses to the collapse of the financial structure have been shaped by what happened in 1929-32.
I think the responses by the WHO and CDC have been prudent, given the nature of influenza. Plus, there has been no serious pandemic on the scale of 1918 since that time, and humanity is overdue for one; it's why Swine Flu in 1976, SARS, or Avian Flu is such a concern. And it ought to be.
May 1, 2009 2:33 PM | Reply | Permalink
Excellent, Jemand, I agree with your comment.
I'd like to add just one thing. Much of the growing resentment in the public sphere is based on a perception that health organizations and authorities are "over reacting" since this manifestation of the virus is very mild.
I would just like to say that the more contained the outbreak is, the less opportunity the virus has to mutate into a deadly strain. While the odds of mutation are very low, mutation becomes more likely with increased infections (i.e. virii population).
Pressure from a disgruntled public CAN prevent civil authorities from, say, closing a school for a week or quaranteeing a confirmed case, so public education about the threat is important.
May 2, 2009 2:57 PM | Reply | Permalink
Hold the conspiracy theories!
While there are obvious incentives to fudge the numbers when companies run drug trials, it's a real stretch to claim that the same applies to WHO and Mexican epidemiologists who are trying to get a handle on this outbreak. What would be in it for them to falsely reduce the casualty count?
It's important to properly distinguish piggy flu deaths from the background noise of deaths that occur for other reasons than piggy flu. I have no doubt that some deaths were attributed to the piggy flu on a clinical basis and that pathology and genetics could not confirm that etiology.
May 1, 2009 2:35 PM | Reply | Permalink
I think what you're missing here is
Was there some incentive to blow this out of proportion, and if there were then who benefits and how?
So far it seems that over 2000 cases in Mexico has been reduced to something like 350. Is that just carelessness plus incompetence, or was there something driving this "flu reporting bubble"?
May 1, 2009 4:29 PM | Reply | Permalink
I think one thing you have to keep in mind is that samples collected in Mexico had to be shipped to a lab in Canada for analysis.
The two earliest California cases were more or less accidentally identified as H1N1. A program that gathered random samples routinely and tested them communicable disease. That suggests that there are other H1N1 infections in the area that were never identified. Also, the virus may have been floating around the border for two or three months.
I think Mexico and California are comparable in terms of response. However, the self-medication habit of Mexicans may be a factor in the difference.
May 2, 2009 2:17 PM | Reply | Permalink
"had to be shipped"
They were shipped to Canada, but that doesn't mean they had to be, it may have simply been routine or maybe cheaper than alteratives. Yes, that took more time (how were samples shipped, overnight, airmail, surface, ...?).
I don't see how "self-medication" figures in. If you mean Mexicans tend not to go see a doctor as often as US folks do, that could indeed be a factor in early under-reporting.
May 2, 2009 3:03 PM | Reply | Permalink
My understanding is that the Canadian government offered to test the samples, and Mexico took them up. I really don't understand your concern - no matter how you shake, bake, rock and roll it, it simply translates that testing should be quicker. It was also delayed in the US, due to various reasons.
And yes, the self-medication issue does mean that Mexicans tend not to go to clinics as a first resort. But at present this just stands as a theory, we really don't know why there were those deaths in Mexico. I imagine we'll know more in the near future.
May 2, 2009 5:29 PM | Reply | Permalink
Sorry Zach.
You say:
"So the "confirmed deaths" and "confirmed cases" numbers seem to be the best thing to focus on."
I disagree strongly.
Since:
Patient Death Number divided by Total Patient Number provides us with the Case Fatality Ratio,
and
Since the number of low symptomatic and recovered cases who will NEVER be counted "probably" vastly exceeds the number of "confirmed cases (meaning laboratory work was completed with specimens taken from patient),
We can only guess at the true CFR for Mexican cases.
However, since all the publicity has made the US VERY aware of this disease (unlike the Mexican situation, where the disease was percolating for weeks or months before anyone noticed, and generating unknown numbers of unrecorded cases):
The United States "confirmed deaths" and "confirmed cases" numbers" are probably "... the best thing to focus on."
O U.S. based deaths divided by 100+ cases equal a CFR of zero, so far.
I'd guess this is due largely to two "potential facts":
That this particular H1N1 virus is not currently too deadly,
and that
In people whom it does make very ill, competent and timely medical intervention reduces the possibility of death. (Unfortunately, we do not know yet what specifically killed the 160 or so Mexican victims -- pneumonia? Cytokine storm? Or ??? It would be GREAT to know, for the future.)
This is not to say that we should be complacent. This H1N1 may mutate to be more deadly, and return with a vengeance.
We must all, at every level for individual to international, be prepared, vigilant, and practical.
But, as much as I love Josh, his site, and, by extension, You -- I beg to differ with your view on this!
May 1, 2009 3:05 PM | Reply | Permalink
John,
You may in the end be correct, but I'd be a little more wary before accepting that because current data indicate the US CFR equals zero, therefore H1N1 is not too deadly. The number of subjects is very small thus far and could represent a skewed sample. I'd like to see N = several thousand before agreeing with your conclusion.
May 1, 2009 3:30 PM | Reply | Permalink
Agree with ya, ptboya.
That's why I said "potential facts," not "facts."
I'll be happier to see the US CFR stay roughly the same as US case numbers rise.
However, it is approaching certitude that the CFR for US cases is VERY different from the original 7%+ CFR from the first "confirmed" Mexico City numbers.
I'm not a statistician, but I'd say that even with our low US N = info, this difference is significant to a high degree.
And thus the CFR in the US cases will prove to continue to be WAY lower than the original Mexican "pseudo-CFR"...
"Skewed sample," you say? I'd say that those words apply even more to the District Federale numbers, than the US ones.
May 1, 2009 3:59 PM | Reply | Permalink
The Mexico numbers have been walked back by at least 50%.
May 1, 2009 6:23 PM | Reply | Permalink
John,
You said "'Skewed sample,' you say? I'd say that those words apply even more to the District Federale numbers, than the US ones."
Agree completely. But that gets back to my original point that we don't have anywhere near apples to apples comparisons between the US and Mexico. Moreover logic dictates that if both US and Mexican samples are skewed, especially if they imply artificially low versus artificially high CFRs, respectively, then the true CFR entirely escapes us at present.
May 1, 2009 7:16 PM | Reply | Permalink
A number of reporters have made mention of the fact that this flu outbreak is actually the combination of four variants. I came across this piece at www.worldreports.org. Mr. Story calls it as he sees it.
THE VIRUS APPEARS TO BE MAN-MADE
This Swine ‘Flu is not a naturally-occurring event, but instead is an Advanced Biological Warfare recombination-DNA-genetically-engineered virus. Young healthy adults seem to be the most at risk. This virus is genetically spliced off the 1918 Spanish ‘Flu.
The New Mexican Swine ‘Flu has elements of DNA from the following: avian 'flu, human 'flu Type A, human 'flu Type B, Asian swine 'flu, and European swine 'flu: a strange combination never seen before and having less than 1/10% chance of being a natural event.
Figure the odds on human and animal viruses from four or more continents suddenly recombining into a new 'flu, during a non-'flu season, that spreads from human-to-human with a 10% estimated prospective fatality rating?
This new 'flu is a lab-created Advanced Biological Warfare DNA genetically engineered virus, and it appears to have been deliberately released. This event is an Advanced Biological Warfare event. It is far more important than 9/11, and, by itself, could bring deaths in such magnitudes as to exceed the number of deaths from all causes in the Second World War.
May 1, 2009 10:17 PM | Reply | Permalink
Residents at the epicenter in LaGloria, Mexico thought the source of their flu was in the filthy, fly-infested lagoons of manure nearby at the huge hog confinement owned by Smithfield Farms, which is based in Virginia. This Guardian article indicates that the residents say the disease started in February (not March or April):
http://www.guardian.co.uk/world/2009/apr/27/swine-flu-search-outbreak-source
I thought the residents' belief that the flies had anything to do with the disease was a bit of a stretch, until I read this article:
http://www.ncbi.nlm.nih.gov/pubmed/16896143?ordinalpos=6&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum
A timeline by Veritect, the company that tracks animal and human infectious disease events all over the world:
http://biosurveillance.typepad.com/biosurveillance/2009/04/swine-flu-in-mexico-timeline-of-events.html
An article about how complicated the SIV, the Swine Influenza Virus, has become in the last several years, stating that swine herds can carry multiple strains at a time, even when the piggers are well-vaccinated:
http://www.porkmag.com/directories.asp?pgID=677&ed_id=2787&component_id=807
A 2006 article by Rolling Stones on Smithfield:
http://www.rollingstone.com/politics/story/12840743/porks_dirty_secret_the_nations_top_hog_producer_is_also_one_of_americas_worst_polluters
I think it's clear that we can expect more scares like this.
May 2, 2009 11:18 AM | Reply | Permalink
There's always some type of new flu. In fact, the flu is different each year. It's why we can get sick each year because the antibodies in our blood are very specific. It's why you have to get a shot each year.
Seems like each year we get a flu with a new name (like "Beijing Flu" a few years ago). I like the President's approach which has been essentially "Remain calm. Take care of yourself. Stay out of public areas if you are sick. See a doctor if you do get sick."
The only pandemic here has been a world-wide soiling of underwear as nearly everyone has collectively wet their pants about a flu that is essentially the same thing we get every year.
May 3, 2009 3:00 AM | Reply | Permalink
Actually convincing the world not to call it Swine Flu is a major victory and reveals the power of the industrial farm sector. Actually there is significant evidence that this flu which is a hybrid of American swine flu, Asian swine flu, human flu and Avian flu either had to be produced intentionally in a lab or was the product of the highly unsanitary conditions under which most of the pigs in the world are raised today. It is not a coincidence that just north of Mexico City in San Louis Potosi is a very large industrial pig raising facility that produces around 900,000 pigs a year and is owned by The Smithfield Foods Company. People living in this area were some of the first to report these health problems and people living in this area regularly commute to Mexico City to work. The New Scientist in an article debunked the theory that this was produced in a lab and strongly suggests that the responsibility for this rests in the lap of the meat industry. So it would seem that this flu has been appropriately named.
May 3, 2009 5:02 PM | Reply | Permalink
Read today that the backlash is starting on many fronts. People are getting a little irked about the gloom-and-doom associated with this flu, which has turned out to be just like any other flu.
My faith in the President was re-affirmed in this situation. He was measured and calm. That's leadership.
May 3, 2009 5:50 PM | Reply | Permalink