ish conquistadors led by Hernando Cortés and Francisço Pizarro, respectively,
resulted in large part from epidemics of smallpox and measles virus infection
that decimated the native defenders. Most of the conquistadors had been
exposed to these viruses in Europe, so were immune to (protected from) their
effects, but those of the New World were completely vulnerable. In fact, nei-
ther the obvious technical superiority of the Spaniards and the superstitions
that Quetzalcoatl or other gods would destroy the natives, nor the Spaniards'
alliances with tribes subjugated by the Aztecs or Incas accounts for the Span-
ish victory. History asserts that the Aztecs, once incited to fight, savagely
attacked and defeated the Spanish. However, on the very evening that the
Aztecs drove the conquistadors out of what is now Mexico City, killing many
while routing the rest, a smallpox epidemic began. As it raged in the city ( 3 ),
not only did the susceptible Aztec forces die in droves, but the psychological
aspect of seeing Spaniards, who fought under a Christian god, resist this new
malady while warriors of the Aztec gods were dying of infection demoralized
the natives even further. The Aztecs could not have known that smallpox was
endemic in Europe at this time and that many in Spain exposed to smallpox
earlier were resistant or immune to subsequent infection by this virus. The
stricken Aztecs interpreted the death of their people while the Spaniards went
untouched as a clear indication that the Christian god held dominance over
native gods. Therefore, one direct consequence of mass smallpox infection
was the subjugation and subsequent exploitation of native Americans and
Mexicans by the Spaniards. A second and more lasting effect was destruction
of the native culture; as the Spaniard culture assumed sovereignty, millions of
Indians were converted to the Christian faith. During the time of the Spanish
conquest in the New World it is estimated that more than one-third of the
total native population had been killed by smallpox viruses.

In addition to propelling the establishment of Christianity in Mexico and.
Latin America, viruses played a role in enlarging the African slave trade
throughout the Americas. African blacks are relatively resistant to yellow fever
virus, whereas Caucasians and native Americans are much more susceptible.
Because so many native Americans had died from yellow fever, too few work-
ers remained to do chores in the fields and mines. The Spaniards then im-
ported black slaves as labor replacements ( 3 ). The net result was expansion of
black slave importation to the Americas ( 4 ); ironically, the yellow fever virus
initially came from Africa aboard trading and slave ships.

In addition to Spain, other European countries staked out colonies in the
Americas. The French colonized Haiti and, in keeping with their observation
that the Africans resisted infection by yellow fever and therefore were stronger

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