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March 7, 2007

Focusing on three deadliest diseases, conference brings together epidemiologists, demographers

By Rahul Kanakia

Epidemiologists are used to studying the spread of disease by looking at biological factors, such as morbidity and the mechanics of transmission. But a recent conference at Stanford, sponsored by the Institute for Research in the Social Sciences, used demographic techniques to model disease transmission.

The Feb. 23 conference, "Demography and Infectious Disease: Integrating Multiple Levels of Biological and Social Organization," focused on how demographic tools can be used to study the ways in which diseases spread. The seven presentations looked at HIV/AIDS, tuberculosis (TB) and malaria, the three most deadly diseases in the world today.

Assistant Professor James Holland Jones of Stanford's Department of Anthropological Sciences discussed how a high incidence of diabetes might lead to new TB epidemics in the developed world. Tuberculosis is transmitted during its active phase, but most people who are exposed to it only develop latent TB, which is asymptomatic and can last for years before becoming active. This slows the spread of the disease, Holland said.

But recent medical research shows that people with type II diabetes may be six times more likely to get TB than those without it. And while most people who are exposed to the disease only have a 5 percent chance of developing active, rather than latent, TB, this percentage may be much higher for diabetics.

Jones created a model showing that if diabetes increases the chance of rapid progression from 5 to 15 percent, it could result in TB spreading much faster than it has in the past. And with the number of diabetes cases in North America standing at around 20 million and increasing each year, he said, conditions may be ripe for a tuberculosis pandemic.

Other talks looked at the spread of HIV/AIDS in China, the biological and demographic causes of HIV prevalence among gay men, sexual behavior in eastern Zimbabwe, the effect of male circumcision on the spread of HIV, the demography of malaria in Africa and the Amazon, and how the influenza pandemic of 1918 affected the prevalence of tuberculosis.

Although social scientists gave most of the talks, the audience also included medical epidemiologists. The closing panel on interdisciplinary research contained representatives from a mix of disciplines, including Jones; Grant Miller, assistant professor of medicine; Edward Penhoet, president of the Gordon and Betty Moore Foundation; Shripad Tuljapurkar, professor of biological sciences at Stanford; and the moderator, biologist and Stanford President Emeritus Donald Kennedy, editor-in-chief of Science magazine.

Miller, who has a courtesy appointment in economics, described how epidemiologists and economists think very differently about health issues. "When a lot of people think about economics and health, they think economists are typically interested in relationships running from population health and individual health to individual socioeconomic outcomes," he said. "But recently, there's been a lot of very exciting work in economics on how economic paradigms of human behavior actually influence health outcomes."

Miller continued, "A lot of economists are starting to propose very simple behavioral dynamics between sexual activity and HIV prevalence rates. For instance, very high prevalence rates increase the costs of risky sexual activity. It starts to challenge notions of what are the most effective ways to control disease."

Participants also discussed the difficulties of pursuing interdisciplinary research within an academic environment that doesn't necessarily reward work at the margins of a field.

"We're still split up by discipline; we still have to get tenure within a department," Tuljapurkar said.

Despite such obstacles, Miller said, "Events like this are very encouraging because they show a deep personal commitment to solving problems. It suggests that even in the absence of a very rigid reward structure to pursue this work, people are going to do it anyway."

Applied Biosystems, a biotechnology company, partly sponsored the conference to celebrate its 25th anniversary. It also has supported one-day conferences on the life sciences in the United Kingdom, Singapore, Japan and Southern California. The next and last conference in the series will be held at the University of Pennsylvania on April 25.

Rahul Kanakia is a science-writing intern at the Stanford News Service.

Editor Note:

A photo of James Holland Jones is available on the web at (slugged "jones_jh.jpg").



Lisa Trei, Stanford News Service: (650) 725-0224,


Chris Thomsen, Institute for Research in the Social Sciences: (650) 799-8843,


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