Monthly Archives: July 2008

Infectious Disease, Uncategorized

Trailing Off of the Epidemic Curve?

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The latest CDC report on the ongoing Salmonella serotype Saintpaul suggests that we may indeed be nearing the end.  Here is the epidemic curve as of 28 July:

28 July Salmonella Epidemic Curve

While there is certainly still the possibility of more cases appearing that have not yet been reported or another introduction (see previous post), the fact that the epidemic curve has continued to trail off in two successive weeks is good news.

The epidemiological evidence continues to implicate fresh jalapeño chiles grown in México.  As of 28 July, 1307 cases have been reported since 1 April 2008. Nearly every state in the union has reported at least one case from this outbreak, as can be seen on this map:

CDC Map of Salmonella Cases 07/28/08

Again the most likely victims (at least to report illness) are 20-29 year-old adults while the least likely to report illness are 10-19 year-olds and those over 80.  Once again, I suggest that this is consistent with a vehicle consumed along with alcoholic beverages. Salsa.  Though contaminated jalapeños (or other produce) could, of course, make their way into other foods as well. The Saintpaul strain was relatively rare before this outbreak, leading CDC to suggest the following:

The previous rarity of this strain and the distribution of illnesses in all U.S. regions suggest that the implicated food is distributed throughout much of the country. Because many persons with Salmonella illness do not have a stool specimen tested, it is likely that many more illnesses have occurred than those reported. 

Let's hope that this outbreak is really coming to an end.  It would be nice if we could identify the source of the infection.  Foodborne disease is an important public health concern that probably does not receive the attention it should.  A 1999 paper by Mead and colleagues (admittedly now a bit long in the tooth) estimated that foodborne diseases cause approximately 76 million illnesses, 325,000 hospitalizations, and 5,000 deaths in the United States each year.  It is not hard to imagine that in the 10 years since this study the foodborne disease burden has increased in the U.S.  Time for another study, I'd say.

Uncategorized

Unusual Editorial

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This is something you don't typically see in the editorial pages of the New York Times, viz., advocacy for reinstating US Air Force investigations of unidentified flying objects.  Pope has a point; closed-mind policies are probably never a good idea.  This is not to say that we have little green men coming to cut crop circles or probe guys in pickup trucks on rural highways.  But if there are things in the air the identity of which we don't know, maybe we should try to figure out what they are?  I guess I'd rather see us fix health care and improve infrastructure first, but I am generally in favor of ridding ourselves of self-induced blind spots.

Diet & Nutrition

The Food Stamp Challenge

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Imagine eating for $3/day.  The U.S. Department of Agriculture estimates that this is the average food stamp for recipients of this federal program.  There is no way that a person can eat fresh fruit or vegetables or whole grains (you know, the things that are supposed to be at the base of the new food pyramid?) on that sort of budget.  A man my age is supposed to eat three cups of vegetables each day according to the USDA. Forget about coffee or tea. One could imagine eating decently if one had the time to spend on food preparation (legume soups come to mind).  However, if you're a member of the working poor, time is not something you typically have a lot of. The American News Project has a video that discusses the problem of hunger in the United States today.  They interview Jim McGovern, Congressman from the Massachusetts 3rd District and a long-time advocate for domestic food security.  I am left wondering, how well would I do eating on $3/day? 

 

Infectious Disease

IMF Structural Adjustments Increase TB Incidence, Prevalence, and Mortality

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A new study has found that the structural adjustments that the International Monetary Fund requires of countries to which it loans money increase tuberculosis incidence, prevalence, and mortality.  The authors studied tuberculosis epidemiology in countries of Eastern Europe and the former Soviet Union that received IMF loans following 1989.  This result suggests that there are real health trade-offs associated with the fiscal austerity that follows an IMF loan.  This research is very welcome because it adds a reasoned empirical perspective to the often shrill debates over the relative merits of IMF policies. Harvard epidemiologist and political scientist Megan Murray and Gary King have written a companion Perspectives piece in the same issue of PLoS Medicine.  There is also a nice news story on it in The New Scientist.

Human Ecology

Cell Phones and Microwaves

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Devra Davis, of the University of Pittsburgh's Center for Environmental Oncology, has an interesting piece posted on YouTube on the possible health risks of cell phone use.  A health scare about cell phone use seems to appear every couple of years but changes no one's actual behavior as far as I can tell.  What is interesting about this short video is how sensibly it incorporates a discussion of risk into the question of the safety of cell phones. Should we stop using cell phones altogether?  No.  Should we think about the potential consequences of long-term microwave exposure to developing brains.  You bet.   

 

Food for thought, particularly on the subject of the appropriateness of cell phone use by children and adolescents.

Human Ecology, Infectious Disease, Statistics

More on Salmonella

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The first produce to positively match the Salmonella serotype Saintpaul was announced today.  A jalapeño chile, grown in México and processed at an unnamed plant in McAllen, Texas, tested positive for the strain of Salmonella that has sickened at least 1237 people since April.  This is the first time that the bug has actually shown up on a sample of fresh produce.  Perhaps it wasn't tomatoes after all, but it is a nice demonstration of confounding in epidemiological inference (tomatoes and jalapeños are commonly served together in the form of salsa, making it difficult to determine which is the actual vehicle for infection if both are implicated). Now the question is where along the production chain the contamination took place and how we can make sure that we bring an end to this outbreak.  All of the news stories and government reports on this topic can be found on the ProMedMail website.  

Conservation, Infectious Disease, Statistics

Update on Salmonellosis Saintpaul

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The Centers for Disease Control and Prevention have just issued a new report on the ongoing outbreak of Salmonella serotype Saintpaul infection. Since April, 1237 people have been infected.  The investigation has continued to focus on raw tomatoes but also jalepeño (and serrano) chiles and cilantro.  This further supports my previous speculation, based on the age profile of the cases, that salsa consumed while drinking alcoholic beverages might be implicated in this outbreak.  Epidemiological investigations are greatly complicated when multiple vehicles that are typically consumed together are implicated.

There is an interesting caution that accompanies the epidemic curve:

Salmonellosis Saintpaul Epidemic Curve

This has to do with the fact that it can be very misleading to read too much into an epidemic curve for an ongoing outbreak. Consider the epidemic curve for the 2003 SARS outbreak in Singapore:

Singapore 2003 SARS Epidemic Curve

Now imagine we were looking at the curve as it evolved on 12 March.  We might have be tempted to say that the epidemic was coming to an end and, man, would we ever have been wrong! There are a couple of things at work here.  First, epidemics often have multiple introductions and while theory tells us that an epidemic curve will be more or less bell shaped, this is based on the assumption of a single introduction.  If you look at the SARS epidemic curve hard enough, you can see several more-or-less bell-shaped components added together.  The second issue with SARS is that there is extreme heterogeneity in transmission.  Patient #1 probably infected 21 other cases, patient #4 probably infected 62.  The great majority of others infected none.  Individuals who infect more than 10 others are what is known as "superspreaders."  There were five in the Singapore outbreak out of a total of 201 probable cases of SARS and 722 suspect cases.  Finally, there is often a delay between when people get sick and when their cases are reported.  This means that the trailing edge of the epidemic curve always looks like it's closing off its bell shape. The full case report for the Singapore outbreak can be found here. 

So, is the current Salmonellosis outbreak on the wane?  Let's hope so, but as CDC warns:

It can be difficult to say when the outbreak is over, because of the reporting delay.   The delay means that the curve for the most recent three weeks always looks like the outbreak could be ending even during an active outbreak. The full shape of the curve is only clear after the outbreak is over.

With a vehicle-borne disease, we don't have to worry about superspreaders, but the fact that we still don't know the source of the infection or the ultimate cause of the contamination is troubling.  Who knows how much contaminated (presumably) produce is lurking out there?  I, for one, will make sure to wash my produce well! 

Uncategorized

American Inequality and Tax Evasion

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There is a terrific new short film from the American News Project on tax evasion by the super rich.  The piece documents Senate hearings on the use of offshore banking as a mechanism for tax evasion by extremely wealthy Americans.  It also includes footage of world's richest man and voice for moral sanity among the rich, Warren Buffett disclosing that the tax rate he paid in 2007 is nearly half that paid by the hourly-wage earning office staff at Berkshire Hathaway. Wow.

Evolution

On Abolishing "Darwinism"

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Olivia Judson has written another installment in her series celebrating Charles Darwin.  In this one, she suggests that we should lose the term "Darwinism" and all its variants.  I think that she argues convincingly that labeling the scientific enterprise of modern evolutionary biology as "Darwinism" implies that the field is static, indeed, "that the subject hasn’t changed much in the 149 years since the publication of the Origin." Of course, nothing could be further from the truth and the obsession with questions of the form "Was Darwin Right About X?" plays into the hands of anti-rationalist, anti-science creationists. 

Frequently, I have been bothered by the cult of Darwin that one finds among a certain kind of evolutionary thinker and it's nice to see Judson calling this out. 

There is an interesting dynamic that played out in the area of human behavioral biology in the late 1980s and early 1990s.  At the time, there was a feud developing between scientists who studied the present-day consequences of variation in human behavior and those more interested in the design of the organ that leads to behavior, the brain.  In a provocative paper written in 1989, Donald Symons of the University of California Santa Barbara suggested that "adaptive design is usually manifested at the psychological rather than at the behavioral level, that measuring reproductive differentials is at best an inefficient and ambiguous way to illuminate adaptation, and that Darwin's theory of natural selection sheds light on human affairs only insofar as it promotes understanding of the psychology that underpins these affairs."  (there's that ownership of natural selection again) Needless to say, this paper did not go over well with people who actually chose to measure the present-day consequences of behavior (e.g., on reproductive success) and a bit of a flame war broke out in the pages of the journal Ethology & Sociobiology (the official publication of the Evolution and Human Behavior Society and later to be renamed Evolution and Human Behavior).

What is so interesting about this debate is how, in good segmentary fashion, the two sides desperately tried to claim Darwin as the founding mythological patriarch of their lineage.  A science true to Darwin's legacy would variously study behavior or study psychology depending upon whether one was a Darwinian Anthropologist or a Darwinian Psychologist (Symons's terms, though I should note that to this day, at least a plurality of evolutionary psychologists reside professionally in anthropology departments). This debate continues, albeit a little less raw.  I list a number of key papers in this debate below.  We read these in my graduate seminar on evolutionary theory in the anthropological sciences. 

So I support Judson's call to drop the term "Darwinism" (or "Darwinian") from our regular scientific vocabulary. As she cleverly argues, we don't refer to fixed wing aeronautical engineering as "Wrightian" aeronautics, despite the fact that the field was established by the Wright brothers. Use of the patronym plays into the hands of  creationists.  It also makes it too easy to forget that evolution is effected by more than simply "Darwin's" natural selection.  There is (the other) "Wrightian" genetic drift. Or mutation. Or even something as prosaic as migration (dare I call it "Cavalli-Sforzian"?). Science should strive to transcend the cult of personality. I, for one, would like to see less political and religious jockeying to see which tradition can be more true to its mythological "Darwinian" patriarch and more focus on actually doing science.  But I guess that just shows that I remain naïve about human nature.

References

Symons, D. 1989. A Critique of Darwinian Anthropology. Ethology and Sociobiology 10 (1-3):131-144.

Tooby, J., and L. Cosmides. 1990. The Past Explains the Present - Emotional Adaptations and the Structure of Ancestral Environments. Ethology and Sociobiology 11 (4-5):375-424.

Betzig, L. 1989. Rethinking Human Ethology: A Response to Some Recent Critiques. Ethology and Sociobiology 10 (5):315-324.

Turke, PW. 1990. Which humans behave adaptively, and why does it matter? Ethology and Sociobiology 11 (4-5):305-339.

Tooby, J., and L. Cosmides. 1989. Evolutionary Psychology and the Generation of Culture .1. Theoretical Considerations. Ethology and Sociobiology 10 (1-3):29-49.