Understanding the basic biology of infectious disease has been a constant at HSPH since its inception. “We’re one of the few schools of public health that has integrated laboratory science and more classical public health disciplines, such as epidemiology and biostatistics. A lot of our work focuses on the interaction of the infectious agent with its host, and how that interaction leads to disease transmission and progression,” said Dyann Wirth, chair of the Department of Immunology and Infectious Diseases. Wirth is also the Richard Pearson Strong Professor of Infectious Diseases—an endowed position named in honor of the School’s legendary explorer/biologist.
The department’s most acclaimed faculty achievement—Thomas Weller’s discovery of how to grow the poliovirus in a cell culture system—was the breakthrough that led to the development of a polio vaccine. As Wirth explained, “The iron lung treated symptoms. But by discovering the biology, we prevented the infection. In the end, prevention always prevails.”
Yet a century after the School’s founding, prevention has continued to be a hurdle for malaria and tuberculosis (TB), two of the top three infectious-disease killers worldwide (rounding out the deadly trio is AIDS). In 2010, the malaria parasite killed an estimated 660,000 people—mostly children—and infected 219 million. In the same year, nearly 9 million people around the globe became sick with TB and some 1.4 million died. Meanwhile, a rising tide of multidrug-resistant tuberculosis—the primary cause of which is the inappropriate or incorrect use of anti-TB drugs—has made the infection difficult and costly to treat.
The causative organisms of malaria and TB have evolved for thousands of years with their human host, perfecting ways to evade our immune system. HSPH has made groundbreaking discoveries on these evasive tactics. “In malaria, we’ve made two major contributions. One is a fundamental understanding of how drug resistance occurs and how it spreads. The other is the application of genomics to understanding natural infection in Plasmodium falciparum, the main malaria parasite, and the implications of that for vaccine development and for elimination and eradication,” said Wirth. “With TB, we have identified in the tuberculosis bacterium every single gene important for the organism’s survival. That discovery has created a tool that opens doors for new drugs and vaccines.”
Another strength of the School is its interdisciplinary approach to infectious disease. In malaria, for example, a “genes to the globe” framework guides work across the University. “At Harvard, there are economists and businesspeople and ethicists and social and behavioral scientists and people in government—all engaged in trying to solve malaria,” Wirth explained. “People in basic science are trying to understand how the parasite converts from replicating in the red cell to being available for transmission by the mosquito vector. At the same time, in business, a fundamental question is how to handle the supply chain. We have insecticide-treated nets and effective diagnostics and medicines: How do we deliver those in the right amount at the right time to the people who need them?”
Infectious diseases, both deadly and chronic, have challenged humanity since our beginnings. As Wirth sees it, that threat is inherent in our coevolution with microorganisms. “For the most part, these infections have been with us long before there was any kind of intervention. The DNA of organisms represents a footprint of history, the cumulative selective forces. The genomes that exist today—be they humans or infectious organisms—are the survivors, the successful descendants of their precursors.”