The same techniques that Neil Ferguson has used to model HMD in animals are shedding light on some of the most common childhood infections, as well as killers such as HIV/AIDS. The Imperial group is involved in an international collaboration with the Joint United Nations Programme on HIV/AIDS (UNAIDS) in Geneva to map this disease, which presents an enormous challenge to modelers.

There are uncertainties about the disease process itself—how the virus interacts with its host—and about the behaviors that will shape the epidemic. As Bernard Schwartlander, head of epidemiology at UNAIDS, notes: People's sexual proclivities "are not stamped on their foreheads."

Ferguson's group is also working on measles, partly because the biology of the disease is relatively well known and detailed historical records of its patterns of incidence are available. He is trying to predict future incidence trends in the postvaccination era, as well as how health scares about vaccines—particularly the controversial combined measles-mumps-rubella vaccine—will affect those trends.

Similarly, Ferguson is analyzing how mass immunization against chickenpox and the resulting reduction in natural immunity to it is leading to a rise in cases of shingles, a closely related (and more serious) adult disease that is caused by the same virus. "Neither exercise would be possible without the sort of macroanalytical tool provided by mathematical models," he says.

He also intends to study how diseases evolve under selection pressures, the two main ones being how a pathogen evolves through interaction with the host's immune system and how it evolves resistance to drugs. In addition to the obvious clinical implications of this research, it will have broader scientific consequences.

As Ferguson explains, "I am fundamentally interested in the population biology of pathogen evolution, because it's a microcosm for evolution as a whole. But since [pathogen evolution] happens on a much faster time scale than in other organisms, you can actually observe it and the processes shaping it directly."  —LS

Photo: AP Photo/Obed Zilwa

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Reprinted from the HHMI Bulletin,
September 2001, pages 14-17.
©2001 Howard Hughes Medical Institute