Throughout history massive disease epidemics have appeared out of nowhere to inflict misery of biblical proportions on the human race. In the 14th century the bubonic plague wiped out one-third of Europe’s population. In this century, the influenza outbreak of 1918 killed 21 million people in a few months. Many readers will remember when summer brought the fear of polio along with the warm weather. The development of antibiotics brought many ancient scourges, such as smallpox and tuberculosis, under control while the Salk vaccine made polio a memory.
By 1967 medical researchers grew so confident of their abilities to defeat infectious diseases that the U.S. surgeon general announced we would no longer have to fear the return of a modern plague. Sadly, this was premature as tuberculosis is now resurgent and new horrors such as AIDS, the Ebola virus and mad cow disease seem to surface almost daily. Are outbreaks of infectious diseases random events that cannot be predicted or controlled? Not according to Dr. George Armelagos, an anthropology professor at Emory University in Georgia. He writes in the latest issue of The Sciences that the human race is largely responsible for the plagues that have inflicted it through the ages. Along with fellow antropology professor Kathleen Barnes and graduate student James Lin of Johns Hopkins University in Baltimore, Armelagos has developed a theory that epidemics have been sparked by three major epidemeological transitions sparked by human interaction with the environment. These three transitions are the change from a nomadic hunting to a static agricultural lifestyle, the development of powerful antibiotics midway through the 20th century, and the change to a global economy that we are experiencing today. Each has affected human populations in ways no one could have foreseen when it occurred.
Up to about 10,000 years ago humans pursued a nomadic existence of hunting and gathering. Diseases came from random encounters with infected animals and these had little chance to spread among the wandering, low-density populations of humans. But as people settled down to farming and population centers grew a number of ways for disease to spread presented themselves. Clearing fields and developing irrigation methods exposed people to disease-bearing species as ticks, mites, flukes and snails. The domestication of livestock provided a pathway for the jump of microorganisms from animals to humans. Milk from infected cows transmitted tuberculosis, wool and hides carried anthrax, while biting insects preying on both spread diseases such as sleeping sickness and malaria. Scavenger species such as rats and mice spread typhus and bubonic plague while overcrowding in cities spread chicken pox, measles and smallpox.
With Alexander Fleming’s discovery of penicillin in 1929, a “Golden Age of Antibiotics” was confidently predicted that would see the end of infectious bacterial-based diseases. Today, antibiotic-resistant diseases are on the rise with TB and staph leading the list. Only one antibiotic is effective against staph and the day may yet return when a simple boil or infected surgical incision could prove untreatable.
Finally, the new global economy has connected disease-prone emerging nations with the entire globe. In 1991, a cargo ship from Asia dumped cholera-contaminated water in the harbor of Callao, Peru. The resulting outbreak affected more than 300,000 people with more than 3,000 fatalities. In this country, coconut milk from Thailand, raspberries from Guatemala, and carrots from Peru have been responsible for outbreaks of food poisoning. With more than 500 million travelers crossing international borders annually, it is only a matter of time before a disease once associated with tropical or poverty-stricken areas of the world will surface in the United States.
Clair Wood is the Bangor Daily News science columnist.