No offense: To viruses and

bacteria, we're just a snack

The recently broadcast documentary "The Coming Plague" and numerous articles have focused on new and emerging diseases and growing antibiotic resistance in diseases once thought to be under control. One methodology scientists use to understand these problems is population biology, the study of large groups of people or parasites, primarily through mathematical modeling.

"Population biology is really a collection of tools, which have been very frequently used by evolutionary biologists and less frequently by people studying disease," said Rustom Antia, assistant professor of biology. "And what's becoming more and more apparent is that population biology is going to be very important in helping us understand, in a quantitative manner, what's happening with diseases."

Antia and Bruce Levin, professor of biology, have been team-teaching the undergraduate course "Population Biology and the Evolution of Disease" for the past two years, although Antia will be teaching it alone next year. The elective course, which attracts primarily senior premed students, is about one-third lecture and two-thirds seminar with active class participation.

Students study the discovery of infectious disease, the effect of disease in human history, the way that vaccinations work and conditions under which diseases will spread or be controlled in populations. Cancer and other diseases are treated as ecological and evolutionary processes.

Students read articles from a collection of original and review literature. "We have a collection of superb, average and really awful articles for them to read," said Levin, noting that the bad articles are used to teach students that the written word is not sacred.

The articles emphasize four subjects: theories of the evolution of virulence in microparasites (primarily viruses, bacteria and protozoa); the within- and between-host population dynamics and pathogenesis of HIV; the within- and between-host population dynamics and pathogenesis of Mycobacterium tuberculosis; and antimicrobial chemotherapy and the within- and between-host population biology of chemotherapeutic agents.

Because the rigors of a premed curriculum usually entail lots of memory and lab work, the "Population Biology" course is often the first time students are doing anything other than passively receiving information, said Levin, noting, "For many, it's a revelation." And since most of students taking the course already have found out whether they've been accepted into medical school, "it's the first course that they have an opportunity to take a course for learning as opposed to grades," he added.

The class involves a lot of work from the students, who have to get used to "the idea that there isn't a fixed answer to a question," Antia observed.

Class material ties in closely with Antia and Levin's current research. Both are interested in the population biology of antibiotic resistance, with Levin working on the population dynamics of bacteria and Antia concentrating on the population dynamics of the immune response.

Although both scientists work with clinicians, they view disease as an ecological and evolutionary phenomenon, "not just some sort of aberration," said Levin. "From the perspective of a virus or a bacteria or a protozoa, we're just a meal, basically-just the source of nutrients.

"So there's an evolution that takes place between us and the few organisms that feed on us," Levin continued. "By understanding how that evolutionary process works, we believe that we will better understand not only the origin of disease but the control of disease."

-Linda Klein