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Infections are mildly correlated to population, with little evidence supporting warming hypothesis from non-experts

Naegleria fowleri is one nasty microorganism.  A member of the amoeba family, it resides in inland bodies of water in North America.  It attacks humans -- particularly young men.  An alarmist report, backed by a non-expert, is proclaiming that global warming may drive infections.  Is this the case?  Let's examine the facts.

I. Background

The amoeba enters via the nose and works its way into the brain where it multiplies, slowly killing the victim.  The time between infection and onset of symptoms is nearly a week and the symptoms are rather nondescript at first -- headaches, vomiting, and confusion.

Once infected, the host's brain is literally eaten alive.  The disease is referred to as PAM (primary amebic meningoencephalitis).
PAM infection
[Image Source: Trevor Haggie]

Since 1962 only one patient (out of 128 confirmed infections) has survived and infection by the deadly parasite -- a 99 percent fatality rate.  In most cases, the infection isn't even caught.  Vanderbilt University medical school professor William Schaffner describes diagnosis as more luck than any other factor, remarking, "It’s not something that’s necessarily touched on in medical school.  You have to really probe what patients were doing in the last several days, you have to ask if they were swimming. Honestly, an accurate diagnosis is basically serendipity."

N. Fowleri
N. Fowleri is a deadly amoeba. [Image Source: CDC]

Given the low rate of infections -- and even lower rate of infections that are recognized before death -- treatment is more guesswork than science.  Patients are administered a cocktail of antibacterial and antifungal compounds.  Jonathan Yoder, an expert with the Centers for Disease Control’s division of parasitic diseases, describes in a recent interview with The Verge, "That’s very frustrating for us.  Did the treatment only work that one time? Does it work at all? Would other treatments work better? We just don’t know."

The potentially bad news is that PAM incidents -- at least correctly diagnosed ones -- are on the rise.  Here's a graph with the # of deaths and state of the death by year:

PAM incidents by year
PAM incidents by year [click to enlarge] [Image Source: CDC]

Notice that there were big jumps in confirmed infections in the 1970s and in the 2000s.  So what's to blame?

II. Hypothesis: Warming is To Blame

The Verge has run a rather alarming piece entitled "Brain-eating amoebas thrive in US lakes as global warming heats waterways".  To be fair they have a source for this -- Travis Heggie, a Bowling Green State University (Ohio) Sports and Leisure professor.  Now Professor Heggie has no professional degrees in epidemiology or microbiology, but he tracks N. fowleri infections as a hobby.

Yet, he speaks authoritatively, telling The Verge, "The climate is changing, and let me tell you, so is this.  If warm weather keeps up, I think we’ll see N. fowleri popping up farther and farther north."

Is warming to blame for the rise in infections? [Image Source: Tehran Times]

The Verge's Katie Drummond writes, "That speculation seems to be reinforced by recent cases of PAM, once a health woe confined to fresh water in southern states like Texas and Arizona. In Minnesota, public health officials were stunned to see two fatalities caused by N. fowleri — both young children — in 2010 and 2012. The cases are the only in state history, and occurred about 550 miles farther north than any previous reported PAM fatality in the US."

The author is correct, two infections have occurred in Minnesota which are the only infections reported in Northern states.  But note that nowhere in the piece do the real experts -- Dr. Schaffner and Professor Yoder -- suggest that the rise in infections is related to warming (a hypothesis fielded by Professor Heggie alone).  Let's dig into whether the rise in infections is truly correlated with warming.

III. The Boy Who Cried Warming (Hypothesis Invalidated)

Let us consider factors that could drive rates of confirmed infections up (along with a suggestion on how it might impact infection rates):
  1. Warming (most N. fowleri resides in water 86 degrees and up)
  2. National population (more people would mean more infections, you'd expect)
  3. Urban population (people use more crowded water resources)
  4. Papers on the disease (more interest means more awareness, more confirmations)
  5. Mutations (hardy strains survive in new habitats)
Let's acknowledge, but toss out #5, as we don't have the data to track that.

To analyze this, let's first compile the rate of infections per decade which peaked from 2002-2011, thus far [Sources: 12].  For #1 let's take the average rise in surface air temperatures over the U.S. on a decade averaged basis [Source].  For #2 we can use widely available census data [Source].  For #3 we can use data from a world clearinghouse [Source].  For #4 we can use Thomson Reuters "Web of Knowledge" Product.

With this data in hand, we simply analyze the correlation of cases per decade versus influence and here is what we find:
PAM Correlation
Actually climate change has the lowest correlation of any examined factor.  The strongest correlations are with the population itself (around 0.86), and more specifically with the urban population (around 0.85).  

I'd be inclined not to discount the relatively high correlation to the amount of peer-reviewed research published per decade, though it's hard to say whether this is a cause or an effect.  Ironically The Verge report hints at this.  Mr. Yoder comments, "I'll swear my life to that — this is being wrongly diagnosed [for bacterial meningitis].  If someone died of meningitis, I’d suggest looking into that case a little more closely ... and looking at where the brain was eaten away at."

A 1970 study shows that for every 16,000 cases of bacterial meningitis, one was actually a misdiagnosed case of PAM.

But even these correlations are highly speculative when one looks at the graph of change in the various variables, scaled to change in PAM infections per decade:

PAM Correlation

Is there an outside possibility that warming is having some affect on PAM?  Perhaps, but it seems unlikely, given that most cases remain in southern states, some of which have actually cooled (like Georgia):
NOAA warming by state
[Image Source: EPA]

Furthermore, while Minnesota is among the states to have warmed more over the past century, Michigan and the Eastern states have warmed at least as much -- yet had no cases.  Michigan and Minnesota have roughly the same number of lakes [Source: 12] over 100 acres -- yet there were no infections in Michigan.

In other words, while N. fowleri is certainly a poorly understood disease and frightening public health threat.  But to blame warming for this disease (or publicize such claims) is highly dubious.  Quite simply put, the correlation is weak, as is the supporting evidence for such a claim.  It appears this is yet another case of crying wolf.

Sources: CDC via Epidemiology and Infection [abstract], The Verge

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RE: hmmmm
By JPForums on 6/28/2013 11:19:42 AM , Rating: 3
What a wonderfully political argument you make. Let's claim 99% of the intellectual crowd (scientist) for ourselves without giving any information to suggest its true. Let's misrepresent what they really say about it. Finally, let's call the opposition insignificant to isolate them and stereotype them into an undesirable group of people willing to "sacrifice the planet and everyone in it for their own short term agenda".

First, if you want to opposition to take you seriously, you have to admit there is opposition. More than just a tiny minority oppose the prevailing AGW theory.

Second, you need to understand their standpoint. You are never going to convince someone they are wrong if you don't even have a grasp on what they believe. I'm not sure how many people have seen the data and dismiss global warming entirely, but there seems to be a serious dispute over how much is due to man's contribution and how much man can do about it. Hence the opposition to AGW not necessarily global warming in general.

Third, if you are going to claim the intellectual high ground, you'd better be prepared to back it up. I don't believe you when you say that 99% of scientist are saying global warming is a serious problem. I might be inclined to believe that 99% of climatologists believe that global warming exists. I'd believe significantly less agree that man has a significant contribution or that man can do much about it. I personally know of more than a few climatologists that think the planet was better off 400 million years ago, when atmospheric carbon levels were over 6000ppm (less than 400 ppm today) and plants flourished So I'd wager significantly more than one percent don't perceive it to a serious problem. Some see it as desirable, some probably see it as a wash, more probably see it as a problem, but not necessarily a serious one.

Finally, you'll get a lot more support if you push a sensible solution to the problem. Blasting the opposition with no solution in mind is a side step at best. There should be no blank checks to do "whatever is necessary" to "save the earth". The earth will be here long after we are gone. What we are really doing is saving ourselves. Therefore, there is an upper limit to what we can reasonably do to keep the earth enjoyable for future generations. You should be selling the opposition on the long term benefits of any course of action.

Point of interest: most reasonable courses of action have auxiliary benefits. Moving over to cleaner sources of energy (hydroelectric, wind, solar, etc.) - You'd have less dependence on foreign oil (I think even the U.S. far right wing can get behind this). It will eventually be cheaper as cost goes down and the prices of non-renewable resources goes up. You'd keep pollution down. Come visit the industrial areas of Bangladesh and east India and you'll see the kind of pollution the U.S. had back in the industrial revolution. Then, you can decide the worth of pollution control.

Researching methods to collect pollution (carbon?) at the output of industrial smoke stacks would be of much greater benefit than simply charging them for carbon credits or forcing them to buy them from others. That's a cost they push along to the consumer without ever really reducing their output. While pollution collectors would also push cost to the consumer, there is a tangible benefit. If someone could find a method for separating the carbon from impurities relatively cheaply, then the output could be put back into production for things like carbon nanotubes and some of the cost could be reclaimed.

There are many other (probably better) examples, but I digress.

RE: hmmmm
By Ammohunt on 6/28/2013 1:22:37 PM , Rating: 2
Let's claim 99% of the intellectual crowd (scientist) for ourselves without giving any information to suggest its true.

Deference of authority; just because one is a scientist doesn't make them more correct then anyone else capable of analyzing data. This is the information age not the 18th century where data and knowledge is freely available not locked away by elitists.

RE: hmmmm
By Strunf on 7/1/2013 8:32:37 AM , Rating: 2
I'm an autodidact type of guy and I partially agree with you, but climatology is so vast that to be able to come up with hypothesis on your own you would need some serious amount of time researching and reading, scientists aren't elitists they are just people like you and me that spent loads of time studying.
While it's the information age I don't think the average Joe is today that much smarter than the 18th century average Joe.

RE: hmmmm
By tng on 6/28/2013 1:34:22 PM , Rating: 1
Good sensible post.

I see this allot in the AGW community as a whole, people take the political rhetoric as scientific method and then discount the actual science behind both the pro and con.

Researching methods to collect pollution (carbon?) at the output of industrial smoke stacks would be of much greater benefit than simply charging them for carbon credits or forcing them to buy them from others.
IMO this is mainly just a way to make money off of peoples fears.

RE: hmmmm
By ShieTar on 6/28/2013 4:03:52 PM , Rating: 3
I personally know of more than a few climatologists that think the planet was better off 400 million years ago, when atmospheric carbon levels were over 6000ppm

So you do know dozens of "climatologists" (not actually a word or occupation) who just happen to hate animals and love the planet and think it would be better of with plants only?

Truth is, the current carbon levels do not allow the antarctic ice shield to remain stable. Sure, its gonna take centuries, or decades at the very least, until New York will finally drown, but it wil happen, and no first-semester climatology, meteorology or physics student (or just any interested high-school student) will really doubt that.

The claim of 99% of all scientist on agreeing on global warming does no longer need any proof today. That topic has been worked out in the 70s and 80s, you are trying to disagree with the absolute basics of modern education here. No, the droughts in Australia and the western US are not random. No, the regular occurence of "Once-a-Century" floods and storms in the eastern US and Europe are not instances of punishment by God. And no, the arctic ice shield is not going away because it is just shy about being photographed by satellites.

The consequences of global climate change in the last 40 years have been quiet exactly been what has been predicted by the scientific community, and any remotely intelligent human being has by now given up any arguments of doubt. Of course the same is true about religion, which we successfully debunked 160 years ago. And nevermind "lending money for interest" which was identified as stupid before even the bible was written.

Some people just insist on sticking with the idiot choice. Good for them. Pity they tend to be better at having big families than the rest of us.

RE: hmmmm
By KoS on 6/28/2013 4:13:10 PM , Rating: 2 expect anyone to take what you have to say seriously? In the first sentence you can't even state correctly what the person you are responding to said.

He said "more than a few" to where you expanded it out to "dozens". Wow! I know kids have problems with math now-n-days. But come on.

RE: hmmmm
By ShieTar on 6/28/2013 4:22:58 PM , Rating: 2
So, in your world, dozens are less than a few?

Yeah, I reworded. I'm rather sure that I did not change the information contained in the original post though.

RE: hmmmm
By KoS on 6/28/2013 5:01:53 PM , Rating: 1
What are you talking about? Where did I say or imply what you are asking?

No shit, a few is less than a dozen(s). Again he said a few and then you stated he was talking about dozens. I think I have a good grasp what the difference is between the two.

No one is saying you changed anything he said, outside of what I mentioned before...a few doesn't equate dozens.

If one can get that correct, then why should I or anyone else believe in your remaining statements to him?

RE: hmmmm
By KoS on 6/28/2013 5:05:20 PM , Rating: 2
If one can' should read in the last sentence.

I have a bad habit of dropping the "n't"..grrr

"There is a single light of science, and to brighten it anywhere is to brighten it everywhere." -- Isaac Asimov

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