Since the dawn of the human race, medicine men and physicians have
wondered about the cause of disease, especially what we call “contagions.”
Numerous people become ill with similar symptoms, all at the same time.
Does humankind suffer these outbreaks at the hands of an angry god or evil
spirit? A disturbance in the atmosphere? A miasma? Do we catch the illness
from others or from some outside influence?
With the invention of the microscope in 1670 and the discovery of
bacteria, doctors had a new candidate to blame: tiny one-celled organisms
that humans could pass from one to another through contact and exhalation.
But the germ theory of disease did not take hold until two hundred years
later with celebrity scientist Louis Pasteur and soon became the explanation
for most illness.
Recognition of nutritional deficiencies as a cause of diseases like
scurvy, pellagra, and beriberi took decades because the germ theory became
the explanation for everything that ails the human being. As Robert R.
Williams, one of the discoverers of thiamine (vitamin B1) lamented, “all
young physicians were so imbued with the idea of infection as the cause of
disease that it presently came to be accepted as almost axiomatic that
disease could have no other cause [other than microbes]. The preoccupation
of physicians with infection as a cause of disease was doubtless responsible
for many digressions from attention to food as the causal factor of
During the Spanish flu pandemic of 1918, the deadliest example of a
contagion in recent history, doctors struggled to explain the worldwide
reach of the illness. It sickened an estimated five hundred million people—
about one-third of the planet’s population—and killed between twenty to
fifty million people. It seemed to appear spontaneously in different parts of
the world, striking the young and healthy, including many American
servicemen. Some communities shut down schools, businesses, and
theaters; people were ordered to wear masks and refrain from shaking
hands, to stop the contagion.
But was it contagious? Health officials in those days believed that the
cause of the Spanish flu was a microorganism called Pfeiffer’s bacillus, and
they were interested in the question of how the organism could spread so
quickly. To answer that question, doctors from the US Public Health
Service tried to infect one hundred healthy volunteers between the ages of
eighteen and twenty-five by collecting mucous secretions from the noses,
throats, and upper respiratory tracts of those who were sick.2 They
transferred these secretions to the noses, mouths, and lungs of the
volunteers, but not one of them succumbed; blood of sick donors was
injected into the blood of the volunteers, but they remained stubbornly
healthy; finally they instructed those afflicted to breathe and cough over the
healthy volunteers, but the results were the same: the Spanish flu was not
contagious, and physicians could attach no blame to the accused bacterium.
Pasteur believed that the healthy human body was sterile and became
sick only when invaded by bacteria—a view that dominated the practice of
medicine for over a century. In recent years we have witnessed a complete
reversal of the reigning medical paradigm—that bacteria attack us and
make us sick. We have learned that the digestive tract of a healthy person
contains up to six pounds of bacteria, which play many beneficial roles—
they protect us against toxins, support the immune system, help digest our
food, create vitamins, and even produce “feel good” chemicals. Bacteria