Philip Alcabes discusses myths of health, disease and risk.

Plague Did Not Begin in China. And Why Should Anyone Think It Did?

Nicholas Wade, the NY Times‘s science writer, jumps the gun with a story today asserting that plague began in China.  Maybe it’s understandable:  you don’t often get a front-page story if you’re a science reporter, so once in a while you take some shaky science and turn it into an international incident.

But to understand why the story is wrong means recognizing a weakness of science as it’s often practiced today.

Wade’s claim is based on two papers published this month.  A relatively well done study by Haensch et al. in PLoS Pathogens earlier in October tested human remains from well-identified plague pits — burial sites for medieval plague victims — in different parts of Europe.  Researchers amplified DNA sequences of the plague bacterium, Yersinia pestis, at specific genetic loci, and tested to see whether the DNA matched known sequences of contemporary Y. pestis genes.

The findings published in PLoS suggest that the Black Death and perhaps subsequent waves of plague in Europe were indeed caused by Y. pestis — which would tend to debunk the theory proposed by some British researchers that the Black Death was some kind of viral hemorrhagic fever outbreak.  And they suggest that there were at least two widely different Y. pestis strains involved in different parts of Europe.  Here’s a bit of the abstract:

[O]n the basis of 17 single nucleotide polymorphisms plus the absence of a deletion in glpD gene, our aDNA results identified two previously unknown but related clades of Y. pestis associated with distinct medieval mass graves. These findings suggest that plague was imported to Europe on two or more occasions, each following a distinct route.

The main weakness here is that DNA could not be amplified from all of the plague pits the researchers studied, but after using alternative means to test the DNA debris against contemporary gene sequences the investigators concluded that the absence of genetic material reminiscent of one strain of Y. pestis was evidence that that strain was not in play in that part of Europe at the time.  Probably right, but stretching the available evidence.

It’s a common mistake, alas.  To paraphrase Karl Popper:  just because you see DNA from white swans and don’t see any DNA from black swans, doesn’t mean that black swans don’t exist.

Still, the PLoS paper is persuasive that more than one strain of the plague bacterium was circulating, and probably causing deaths, in the plague period in Europe.  Of course, it says nothing about China.

So where does the NYT reporter get his headline-grabbing story?  A paper to be published in Nature Genetics online (still embargoed at the time I’m writing, but a summary appears here) states that the sequences of plague DNA amplified from plague pit remains, as well as contemporary isolates, can be placed on a molecular clock because of the occurrence of unique mutations.  Winding the clock backward, the researchers conclude that the Ur plague organism, ancestor of all Y. pestis, came from the far east.

The molecular biology may be unimpeachable, but the inferences about history aren’t supportable by molecular evidence.  That might explain why they’re almost certainly wrong.

The problem (scientists, I hope you’re listening!) is that you may know very well what you know, but you can never know what you haven’t seen.  The hereditary tree has its roots in China.  Here is one proposed by some of the same authors in a 2004 PNAS paper:

In this set-up, isolates of Y. pestis from China seem closest to the primordial strains.

But of course, the molecular clock doesn’t take account of strains that are no longer extant.  And ones that haven’t been unearthed.  The contemporary researchers don’t see them (or don’t know how to look), so they don’t exist.

It’s a bad mistake, inferentially.  And historically.  It’s where the NYT writer goes wrong.  Almost certainly, plague did not begin in China.  It began as an enzootic infection of small mammals in the uplands of central Asia.  This is the story convincingly relayed by William H. McNeill in Plagues and Peoples a generation ago, and none of the many accounts I’ve read since then has debunked it.

Plague would have had to begin in an ecosystem in which it could circulate at moderate transmission rates with little pathogenicity among small mammals (the natural host of the bacterium).  Exactly where it started remains open to question, but it was probably in the area that is now Turkestan/Uzbekistan.  With the development of trade between that region and China, intermixing of local (central-Asian) animals with caravan-accompanying rats would have allowed Y. pestis to adapt to the latter.

Quite possibly China was the source of the first human outbreaks of plague — because the river valleys of China were settled and agricultural (therefore offering feeding opportunities for rats as well as multiple opportunities for rat-human interaction) long before Europe was.  That fact probably accounts for the biologists’ (mistaken) belief that their early samples show that Y. pestis started out in China.

But plague began as — and remains — a disease of animals.  To acknowledge that human outbreaks in China preceded the human outbreaks in Europe (the Justinian plague that began in the mid-sixth century, the Black Death that began in the 1340s, and subsequent visitations) is not the same as saying that plague originated in China.

Which it didn’t.  Plague is an animal disease from Central Asia.  Plague’s long history is the usual one:  ecosystem change, trade, animal-human interactions, alterations in climate and economic conditions, and occasional opportunities for mass human illness.   (One world, one health.)

Above all, remember that science is only capable of drawing conclusions about what scientists can observe.  Don’t be taken in by hair-raising stories.  Even in the NY Times.

By Philip Alcabes | October 31st, 2010 | Categories: climate change, Disease, epidemics, Narratives, science, Uncategorized | Tags: , , , | 3 comments

A Must-Read Book

I urge you to stop what you’re doing and read Rebecca Skloot‘s The Immortal Life of Henrietta Lacks (Crown, 2010).   It’s a rare combination: clear reporting on how medical science works, insightful consideration of deep moral issues about the uses of human tissue for the advancement of knowledge, and a moving, often troubling, family narrative.

Henrietta Lacks died of cervical cancer in the “colored” ward at Johns Hopkins Hospital, in 1951.  From samples of her cervical tissue, the immortal cell line called HeLa was developed (by Dr. George Gey, at Hopkins).  Skloot’s story covers the family’s travails before and since, but also digs deep into the problem of race in the business of American medicine.  Her account challenges, or should move us to challenge, the smug certainties about our supposedly post-racial society, and the convenient formulae about “informed consent” and “access to care.” I guess I should say, The Immortal Life should make us ask just what “care” means in today’s system.

Henrietta Lacks and her family members were almost never taken seriously as humans with real problems.  First, they were poor and uneducated black people from tobacco country relocated to Baltimore; then, they were the bearers of the same genes as a woman (Henrietta) who had died of a remarkably aggressive, and therefore medically interesting, cancer; later, they were background and local color to the story of the origin of the thriving, and therefore scientifically interesting, HeLa cell line.

To Skloot’s credit, she’s taken to heart, and acted on, the problem:  she founded the Henrietta Lacks Foundation to help raise funds for education and medical expenses for Henrietta Lacks’s family.  Skloot’s blog, Culture Dish, carries updates about some of the achievements of the foundation and sometimes takes up issues germane to the book, especially regarding personal rights to genetic information (here, for instance).

It’s also impressive that Skloot interweaves in her narrative (and takes up more fully and explicitly in an Afterword) the vexing question of ownership of tissue samples.  She highlights how the expanding capacity to extract information from genetic sequencing ups the ante on the questions of privacy of tissue samples — since it’s now possible to ascertain potentially identifying information from genetic sequences even in a sample from which the usual verbal identifiers (name, address, and so forth) have been removed.  And she asks how the profits potentially available from exploitation of new discoveries should be shared.

The intersection of these problems with the matter of race makes The Immortal Life of Henrietta Lacks, like James Jones’s Bad Blood and Harriet Washington’s Medical Apartheid, a book that should be required reading for everyone involved in the health sector today.

By Philip Alcabes | August 20th, 2010 | Categories: books, Ethics, Health Professions, Myths, Narratives, Physicians, science, Uncategorized | Tags: , , , , , | Comments Off

Media Culture: Beyond Fat and Salt?

Over at Media, Culture & Health, Steven Gorelick notes that a story on salt and the food industry, which appeared on page A1 of the print NY Times on Sunday, would not have made the front page in the past.

What has changed?  How does the story of wrangling over the sodium content of American food merit space in the main news sections of the most influential media — even the front pages of the NY Times or LA Times?

1.  One answer is that health occupies much of the American conversation today.  A visitor from another planet watching our TV news shows or reading the main newspapers would have to be forgiven for thinking that Americans are dying from a multitude of irrepressible disease threats.  We can’t seem to stop talking about how to improve our health.

(In fact, as Michael Haines notes at the Economic History Association website, U.S. life expectancy almost doubled between 1850 and 1960, from 39.5 years to 70.7 years; since then it has increased slowly, and is now estimated to be about 78.2 years.  In other words, health wasn’t a matter of news much during the time when longevity was improving dramatically, in the late 19th century and first half of the 20th.  By the time health became a cultural preoccupation, the majority of Americans were living well past middle age.)

2.  Another answer, perhaps more important is that when we talk about health today we mean personal responsibility.

When I began studying epidemiology, in the late 1970s, public health essentially meant disease control.  Yes, lip service was paid to so-called health promotion — much was made of the World Health Organization’s definition of health, promulgated in 1946:

Health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.

But no metric for complete well-being was widely recognized.  And the usual epidemiologic measures of incidence and mortality rates, life expectancy, and so forth seemed to work just fine as ways of understanding why some groups of people lived longer and more capable lives, while others lived miserably and died young.

Sometime since then, the health sector, including public health, has turned to individual responsibility as the key to well-being.

If each of us is responsible for his or her own health, then it’s our own fault if we get sick.  Naturally, advice abounds:  buckle up, use a condom, eat less fat, know your cholesterol level, wash your hands, use mosquito repellent containing DEET, wear sunblock, eat fresh fruit and vegetables every day, lower your stress.

The advice adds up to this:  know your limits.  Federally sponsored research tells us that self-control is ontagious.

The personal-responsibility view of health says, “control your appetites.”

3.  But let’s think about another change:  more people are concerned about the American diet.  As noted last week, the food movement has given us ways to think about eating that go beyond the tiresome story of obesity and hypertension — Beyond Fat and Salt, you could say.

Of course, the main media outlets still tell the food story in Fat-and-Salt language, as the news articles in the NY Times, LA Times, and others show.  It’s the food industry vs. the foodies, or the food industry vs. public health, or the food industry and public health vs. appetites — anyway, somebody against somebody in the name of health.

The media aren’t quite past obesity and hypertension yet.  But as the culture moves beyond obsessive self-inspection in the name of health, no doubt media will, too.


By Philip Alcabes | June 3rd, 2010 | Categories: Behavior, Disease, Health Professions, Narratives, News, obesity, public health, Uncategorized | Tags: , , , , , , , | 2 comments

Putting Obesity in Perspective

Michael Pollan’s essay in this week’s NY Review of Books offers a framework for looking at modern food and eating.  If public health advocates took Pollan’s perspective, the vitriol of their anti-obesity crusade could turn into a force for real social reform.

Reviewing five books on what he calls the “food movements,” Pollan notes the widespread discontent with contemporary industrialized food production (I’ll call this “American eating,” although its dominance is increasing around the world).  And he suggests that its common theme is cultural discomfort. The food movement, Pollan argues, has “set out to foster new forms of civil society”:

It makes sense that food and farming should become a locus of attention for Americans disenchanted with consumer capitalism.  Food is the place in daily life where corporatization can be most vividly felt…  The corporatization of something as basic and intimate as eating is, for many of us today, a good place to draw the line.

This is a refreshing insight.  It’s thankfully broad, taking  the focus away from health, and therefore from the anti-obesity crusade and the “toxic food environment” view promoted by health advocates.

But Pollan’s perspective is especially refreshing because it renews the conversation about our private lives — particularly the extent to which we’ve ceded our innermost values to the demands of corporate profit and government policies.  And those demands, as Marion Nestle often points out (recently here), are generally linked.

Pollan reminds us that our innermost values are literally innermost:  they have to do with what goes into our stomachs.

I’ve already stated my argument that the anti-obesity crusade is really about control, not health (see here and here).   The crusaders do cite “public health” as a rationale for the war against obesity.  But when they describe what’s wrong, they do so in terms that are sometimes medical (diabetes, hypertension), sometimes technical (serving sizes, calorie counts, the infamous toxic food environment), and sometimes medieval (gluttony, laziness).  Their inability to articulate the source of the problem is a signal that they’re sure something is out of control but unsure exactly what.

The public health approach to obesity is a failure.  It doesn’t let us talk about what needs to be reformed.  And it’s often allied with efforts to make sure the poor stay poor — even though wealth inequality is surely part of the problem in the first place.  The public health industry’s demands for additional regressive taxation in the form of increased “fat” taxes on sugary beverages or high-calorie foods reveal its preference for the status quo.  Make the poor pay more for their soda and fast food; that will make them think twice about supporting industries that are making us fat.

Even well-meaning public health professionals who advocate government intervention against low-price-but-low-nutrition food  as a way of curtailing obesity ignore the central role of food and eating to liberty and happiness — they’re interested primarily in how many additional years of life (however unhappy) could be purchased by trading in the fries in favor of broccoli.  Or, worse, they’re interested only in the dollar costs to taxpayers — in terms of hypertension and heart disease — of tolerating obesity.

Pollan, today’s most thoughtful and insightful philosopher on the subject of food and eating, offers a more satisfying view.  Sure, you may want to change American eating because you think obesity is bad for people’s health.   But you might want to change eating simply because the food scene is distressing, because it crystallizes and exemplifies the many ways that we give over our private (innermost!) moral decisions to the influences of corporate/consumerist thinking.  You might want to change it because, as Pollan reminds us (in regard to a new book by Janet Flammang), the dominance of American statecraft by corporations allows the preparation of food to be relegated to the least valued, least powerful, and lowest paid workers.  You might want food to taste better — valuing pleasure over longevity.

With Pollan’s broad view, you  don’t have to join the anti-obesity crusade.  You don’t have to speak the technical language of risk.  The common language of freedom, desire, and pleasure will do.

By Philip Alcabes | May 26th, 2010 | Categories: Behavior, epidemics, Health Professions, Narratives, obesity, public health, Risk, Uncategorized | Tags: , , , , , , | 2 comments

Questions on World AIDS Day

Today is World AIDS Day.  After thirty years, 25 million deaths, and countless articles, books, press releases, TV and radio programs, fundraisers, AIDS walks, and messages from Bono  –  there’s still an AIDS Day?  It’s hard to see how any disease could be less in need of a boost to awareness.

But how can every day not be AIDS Day?  Over 5,000 people die of AIDS each day, worldwide — even now, in the era of effective therapy.  In south Asia alone, more people die of AIDS every two weeks than have died of the H1N1 swine flu worldwide in the past six months (about 8,000).  In Africa, AIDS takes that toll every two or three days.

AIDS is a big problem in far-away poor countries, in other words.  But unlike the usual poor-nation problems that are easily ignored in comfortable North America — malaria, sleeping sickness, dengue, diarrhea, and more — AIDS is still a problem here, too.   Surely, you might think, we ought not to need any reminders about AIDS.

Much has been said about AIDS, and much has been done.  What does World AIDS Day add?

A harder question, perhaps: why can’t AIDS just be an ordinary disease? Surely, you might think, it isn’t special anymore.

Here are some thoughts on the problem of ordinariness, published in the American Scholar a few years ago.  The occasion was the 25th anniversary of the announcement of the first U.S. cases of AIDS.

By Philip Alcabes | December 1st, 2009 | Categories: Disease, epidemics, Myths, Narratives, public health | Tags: , , , | Comments Off

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