Microbial diseases have undoubtedly played a major role in
historical events, such as the decline of the Roman Empire and the conquest of
the New World. In 1347, plague or Black Death struck Europe with a brutal
force. By 1351, about 4 years later, the plague had killed one-third of the
population (about 25 million people). Over the next 80 years, the disease has
struck repeatedly, eventually wiping out 75% of the European population. Some
historians believe that this disaster changed European culture and prepared the
way for the Renaissance. This is just an example from many such epidemics,
which while being devastating in their scope spared not even the high and
mighty of the times.
Apart from the bubonic plague,
measles (now thankfully extinct) and smallpox too played their roles as
epidemic diseases causing high mortality and morbidity. The first recorded
epi-demic of smallpox was in the year 1350 BC in Egypt. The dis-ease was
unknown in the population of the New World until the Portuguese and Spanish
explorers made their appearance. Smallpox then traveled across America,
devastating the previ-ously unexposed population. It was already known at that
time that the disease spreads through the skin lesions and scabs, and that
survivors of the infection were immune to reinfection on further exposure.
Though adopted much later in America and Europe, the practice of inoculation or
variolation, whereby people were intentionally exposed to smallpox to make them
immune, was already being practiced in India, China, and Africa for centuries.