In recent decades, public health agencies have posted alarms about SARS and avian flu, which is slowly reaching from Asia to parts of eastern Europe and now to Africa. Are these worldwide waves of human disease, known as pandemics, likely to increase in the 21st century?
Past human pandemics have given adequate reason for such concern, because of the known ability of bird influenza virus and human influenza virus strains to recombine and form highly potent viruses capable of devastating human populations. Such was the case in the influenza epidemics of 1957 and 1968. Recognizing that such viral propagation results from direct human-to-human contact, and given the increasing level of contact in a modern world, it is reasonable to assume that the frequency of human influenza pandemics will increase.
Perhaps of even greater concern is the fact that geophysicists are alarmed about the earth's current instability and consistently warn of increases of catastrophes such as earthquakes, tsunamis and volcanic eruptions. These circumstances result in human crowding, exposure to temperature extremes, poverty and unsanitary living conditions. Each of these factors, all magnified by the additional deleterious effects of global warming, has been identified as a major promoter of epidemic disease in humans. These conditions also prevail in time of war.
Human sexual behavior has been an increasingly prominent factor in propagation of epidemic disease. Human immunodeficiency virus (HIV) and its consequent colossal AIDS pandemic have enhanced global concern for sexual transmission of disease. Human hepatitis viruses and all herpes virus strains increasingly are recognized as having been acquired through sexual contact. There appear to have been few successful means, on an international basis, of eradicating such chains of viral transmission, although appropriate education has had some impact.
As the population grows and enters the forests and jungles of the earth, humans are coming into contact with indigenous animal species and agents of epidemics in those species. HIV, many of the hemorrhagic fevers, Ebola virus and hantaviruses -- all relatively new to the human species -- are examples. Most likely, such contact will continue to increase.
In the past, as new or advancing infectious disease has become apparent, medical efforts have achieved the means for suppressing, curing or preventing it. In most circumstances, these advances have been made by pharmaceutical companies, which develop their products at very high cost; however, incentives for such development have been reduced over the past few decades. Unless government funding is provided, agents that can stop the progress of epidemic disease will no longer be rapidly forthcoming. For example, tuberculosis is resurfacing at an alarming rate in the United States, simply because emerging resistant strains are no longer susceptible to the drugs that previously were developed.
The multiple factors at play in today's rapidly growing world portend a greater and greater probability of an increase in the frequency of major, uncontrolled epidemics in human populations. Presumably, the trends could mostly be reversed with advances in scientific/medical research that is unhampered by current funding restrictions.
William D. Hillis
, BS '53, MD, is the Cornelia Marschall Smith Distinguished Professor of Biology.