Page 196 - Berkshire Encyclopedia Of World History Vol Two

diseases—overview 545

Some of these, like smallpox and measles, were highly asia at nearly the same time, inflicting severe damage
lethal; others like mumps and influenza were milder. No both on the Roman and Chinese empires. But surviving
one knows when or where they made good their transfer records say little or nothing about lands in between, and
from animal herds to human hosts, but it is certain that guesswork is useless. By contrast, we know that the
it took place somewhere in Asia, perhaps at several dif- Americas were exempt from these herd diseases until the
ferent times and places. It is equally sure that they could Spaniards arrived, and the same was true of other iso-
only do so in and around cities, thus becoming distinc- lated populations around the globe. Consequently, in the
tive new “civilized” diseases. sixteenth century, when European seamen began to
Their arrival had paradoxical effects. By killing off encounter people lacking immunities to these diseases,
urban dwellers, they soon made most cities so unhealth- massive die-offs regularly ensued.
ful that they needed a stream of migrants from sur- By then the agrarian peoples of Eurasia had another
rounding villages to sustain their numbers. Yet these twelve hundred years of disease exchange and exposure
same diseases also created a new and very powerful behind them. One well-known episode came between
advantage for disease-experienced populations in con- 534 and 750, when sporadic outbreaks of bubonic
tacts with previously unexposed populations. That was plague ravaged Mediterranean coastlands, only to disap-
because among peoples who lacked acquired immunities, pear for the next six centuries. The historian Procopius
herd infections spread like wildfire, killing adults as well wrote an exact description of the initial onset of that
as children. In the modern era, initial exposure to measles plague, explaining that it came by ship and originated in
or smallpox commonly killed off something like a third Central Africa. Other factors were in play, for modern
of the entire population in a few weeks, leaving survivors studies show that bubonic plague is spread normally by
dazed and distraught and quite unable to resist further bites of rat fleas, which transfer to humans only after their
encroachment by the disease-bearing newcomers. The normal hosts die of the disease. The domestic rats in
effect was multiplied when successive civilized diseases question were probably native to India, and in 534 were
followed one another in rapid succession. Smallpox, relatively recent arrivals in Mediterranean coastlands.
measles, influenza, and even the common cold could all The infection itself was at home in underground bur-
be, and often were, lethal. rows of various species of rodents in Central Africa and
Before that drastic pattern could establish itself gener- northern India, where it behaved among rats like a child-
ally, different centers of civilization had themselves to sur- hood disease and became a lethal epidemic only when it
vive the arrival of these infections from wherever they first invaded inexperienced populations of domestic rats and,
started. Everything about the initial spread of herd dis- of course, humans. But under those circumstances it was
eases within Eurasia and Africa remains unknown, but indeed highly lethal.
disease disasters that ravaged the Roman empire between Procopius says that when the disease first struck in 534,
165 and 180 CE and a second time between 251 and ten thousand persons died daily in Constantinople for
266 probably register the arrival of smallpox and measles forty days. Loss of population and wealth were certainly
in Mediterranean lands, brought back by soldiers return- severe and prevented the Byzantine emperor Justinian
ing from Mesopotamia. Written records also show that (reigned 527–565) from reconquering the richest prov-
China suffered unusually lethal epidemics in 161–162 inces of the western empire, which he had started to do.
and again in 310–312. Germanic and northern Europe escaped this bout
It looks therefore as though extended contacts within with plague, probably because rats had not yet estab-
Eurasia, arising from the establishment of the so-called lished themselves there. But in the so-called Dark Ages
Silk Roads that connected China with Syria, allowed other serious epidemics, including smallpox, measles,
highly lethal outbreaks to occur at both extremes of Eur- and influenza, did break out in the north from time to