Sociopolitical and Environmental Causes of Disease

Garrett notes that epidemic disease is often influenced by sociopolitical behavior and human interactions with the environment. As people seek to subdue nature, microscopic natural forces—namely infectious microbes—respond with their own survival tactics.

Bolivian hemorrhagic fever jumped from mice to humans when human croplands encroached on the mice’s rainforest habitat. The corn crops planted in former rainforest space provided plentiful alternative food for the mice, allowing the population of disease-carrying mice to explode in close proximity to humans. Urbanization allowed bacterial infections such as bubonic plague, Hansen’s disease, tuberculosis, cholera, and syphilis to become endemic in a way that would never have been possible in less concentrated populations. As Garrett describes it, “the more Homo sapiens per square mile, the more ways a microorganism could pass from one hapless human to another.”

War and civil unrest can cause disease as well as environmental and economic devastation. In the aftermath of World War II, mosquito-borne dengue fever was carried across Asia by refugees and armies, while mosquito-control efforts generally came to a halt. Civil war in Nigeria delayed deliveries of antiserum for Lassa fever in 1970, leading to the death of an investigating doctor. Atrocities under the Amin regime in Uganda led to famine, refugees, a devastated economy, and a series of public health epidemics. Military upheaval occurred alongside urbanization, increases in poverty, and sharp population growth. The AIDS epidemic in Africa emerged because of “a change in the interaction between the agent, the host, and the environment.”

Garrett views health as a human rights issue, with poverty, unrest, and social marginalization making people more vulnerable to disease. Unfortunately, despite multiple lessons from the past, many human populations have failed to learn to care for their environments and coexist in equilibrium with the microbes around them.

The Changing Field of Medicine

Trends in medical education and treatment can contribute to disease as well as health. With the emergence of antibiotics in the middle of the twentieth century, medical education de-emphasized infectious disease and parasitology, believing those fields to be nearly obsolete. With generations of medical professionals encouraged instead to study and specialize in chronic disease, physicians were unprepared for the development of antibiotic-resistant bacteria. Indeed, physicians contributed to the development of resistance, as fear of lawsuits led them to over-prescribe antibiotics, placing individual health over public health. By 1992, when drug-resistant TB had become epidemic, there were fewer than fifty TB specialists in the USA.

Research into DNA helped scientists understand microbe evolution and the development of drug resistance. Quick to monetize, labs began to genetically engineer everything from retroviruses to cash crops. The diverse scientific teams that had successfully investigated epidemics in the 1960s and 1970s saw the genetic revolution as

a mixed blessing: on one hand it offered new tools for solving microbial mysteries, but it was also immediately obvious that funding—never generously available to parasitologists or infectious disease researchers—was becoming even scarcer as resources shifted toward molecular pursuits.

The trend of specialization over generalization intensified, yet it was generalists with a broad base of skills who had the most success in the field when an epidemic struck.

The field of medicine, Garrett suggests, is not immune to the human tendency to look for the easy way out. Every disease-fighting tool becomes overused, blunting its usefulness, while the hunt for profits outweighs the greater good. Changes in medicine over the twentieth century have saved many lives, but have also left us vulnerable to the emergence of epidemics. Surveying these trends, Garrett asks,

If AIDS could emerge so successfully worldwide in the age of...