How Medieval Practitioners Thought Diseas e Was Transm itted

During the Middle Ages there were many theories on what caused
disease to spread. Some thought ailments were caused by the wrath
of God; others thought witches and demons sent illnesses. Many believed in a strong astrological influence on life, and they felt
that the planets and stars sometimes aligned to create bad health
among people on earth.
A few realized that swamps, filthy water,
and areas where animal carcasses were left to decay could spread
disease, but they didn’t understand how these conditions gave rise
to illness. They thought this environment led to spontaneous generation
of some diseases by miasma (a cloud of noxious vapors
emitted by the earth or formed in swamps or other areas of decay).
This contaminated the air and water and could make people ill.
Attributing illness to a specific cause gave people a feeling of
control over their lives, and if no other explanation presented
itself, scapegoats often received the blame. Lepers and other “evil
people” were thought to poison wells or take other actions that
spread disease, and of course, if a scapegoat was identified, the
townspeople made that person’s life miserable.
The discovery of microbes did not occur until Antoni van
Leeuwenhoek (1632–1723), a Dutch cloth merchant whose hobby
involved handcrafting microscopes, eventually saw “little animacules”
through the magnifying lenses he created. Even then, scientists
of that day had no understanding about the role microbes
played in disease. Bacteria and its part in spreading illness were
not even suspected until the 18th century, and it took until the
19th century for the theory to be accepted.
Despite not understanding how illness spread, medieval people
realized that diseases could be contagious, and this led to some
customs that helped reduce the spread of illness. Inhabitants of
port towns began to note that when ships from out of the area
arrived with crewmen who were sick, sometimes these men came
on shore and townspeople soon suffered similar symptoms. As a
result, port cities developed a rule that required ships to anchor
offshore for up to 40 days before the crew could come on land.
This method was first used in the ports of Italy and southern
France in the late 14th century as an effort to combat recurrences
of the bubonic plague (the Black Death), and the word quarantine
is derived from the Italian word for a period of 40 days. Later on,
quarantines were used to require sick people to stay in their homes for a period until they recovered or died. (As recently as the early
20th century, towns in the United States still quarantined people
in their homes for illnesses such as scarlet fever.)