YSM Issue 86.1

FEATURE
EPIDEMIOLOGY
Ruthless Microbes:
The Worst Epidemics in History
BY ANANTH PUNYALA
Plagues are perhaps the most relentless,
egalitarian killers that humanity has ever feared;
in fact, many of the worst not only killed, but
also brutally sculpted the history of whole generations
and regimes. Breaking through power structures,
destroying entire populations and often even ushering
in their own virulent successors, diseases on a mass
scale have truly painted the violent history of our
planet. Below are history’s most notorious diseases,
in roughly increasing order of the chaos they caused:
1. The Archetypal Plague: The Black
Death
Courtesy of the International World History Project.
2. The Contagious Conquerer: Smallpox
Historians believe smallpox was first seen in the
mummy of Ramses V and later in Indian records
from 400 AD. The virus enters the respiratory
tract and passes to the liver through blood before
reaching skin cells but can also be passed through
direct skin-to-skin contact. After two weeks,
patients experience delirium and diarrhea before
severe fever and a raised pink rash that turns into
crusty, bumpy sores that hemorrhage. It yields a
roughly 30 percent mortality rate.
Historically, smallpox was the Spanish conquest’s
greatest ally in the 15 th and 16 th centuries,
wiping out over 57 percent of the native population
of Santa Domingo. It went on to crush half
of the Cherokee Indian population by 1738. After
WHO mass vaccination in 1967, scientists isolated
the last case in Somalia in 1977.
Jump back to mid-14 th century Europe. As
small towns consolidate, a pandemic approaches
from the east. Caused by the Yersinia pestis
bacterium, the Black Death arrived via the Silk
Road, carried by fleas living on the black rats
of merchant ships. Victims grew buboes (black
swellings in the armpits, legs, and groin), which
filled with blackened blood tinged by greenish
scum.
The plague reduced the world population of
roughly 450 million by 75 million before rats
were identified as the vectors and were heavily
exterminated. In England, people grew disillusioned
with the Church and, with the scarcity
of labor brought on by the Black Death, gained
a deeper sense of self-worth, ultimately leading
to the English Reformation.
32 Yale Scientific Magazine | January 2013
Courtesy of the New York State Department of Health.