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Chapter 1 ่บซไฝใป็
ๆฐใจๅฅๅบท
่บซไฝใป็
ๆฐใจๅฅๅบท [1] 3
ferocious attacks of zoonoses, animal infections that can be transmitted to
humans. Being new to people, the germs often caused far worse symptoms
1
ๆป่ณๅป็งๅคง
than those in their usual hosts. Therefore, any deadly human infection should
be suspected of being recently acquired by our species.
1
โโ
From Man and Microbes: Disease and Plagues in History and Modern Times by
Arno Karlen, Tarcher
็ฎๆจ20ๅ
ๆณจ savanna: ใตใใณใ
yellow fever
predator
ๆฌกใฎ่ฑๆใ่ชญใใงใไธใฎ่จญๅใซๆฅๆฌ่ชใง็ญใใใ ("ๅฐใฎ่ชใซใฏๆณจใใใใ)
The first big shock to influence human disease patterns was our ancestors'
descent from the trees to the ground, about five million years ago. Perhaps this
happened when Africa became drier, and savannas" replaced forests. This
descent brought changes in our ancestors' diet, lifestyle, and burden of disease.
As a species with our feet now firmly on the ground, we tend to think of
territory horizontally. However, every environment has significantly different
vertical zones. In a forest, certain species of mammals, birds, and insects
require the sunlight and food in the leafy treetop layer; others need the shade,
moisture, and food on the ground; several intermediate zones may exist
between earth and treetops. Moving its usual location only a few meters can
radically alter a species' prey, predators, and germs.
Today, for example, we often see diseases invade new vertical zones. In
Central and South America, mosquitoes infect treetop monkeys with the yellow
fever virus. The disease remains isolated in the top forest layer because
monkeys and mosquitoes there rarely travel lower. The commercial demand
for tropical timber has sent loggers into the forests, and when they cut down a
tree, clouds of mosquitoes come to earth with it. The mosquitoes then feed on
the warm-blooded animals nearest at hand, the loggers, and transmit the virus.
On returning home to cities, the infected workers set off urban epidemics of
yellow fever.
After our ancestors' descent to the ground exposed them to new diseases,
the change in their diet from plant protein to include meat, as they became
hunters, brought about another change in disease burden over the next tens or
hundreds of thousands of years. In each new ecosystem, travelling hunters met
new prey, new vectors (disease carriers), and new parasites*. The result was
parasite 344
ๅ1 ๆฃฎๆใฎ "vertical zones" ใฏ, ็จฎใฎ็ๆ
ใซใฉใฎใใใชๅฝฑ้ฟใๅใผใใฆใใใใ
ๅ2 ้ป็ฑ็
ใฎๆต่กใฏ, ใฉใฎใใใซใใฆ้ฝๅธๅฐๅใซ่ตทใใฃใใจ่ฟฐในใใใฆใใใ. ็ฐก
ๆฝใซ่ชฌๆใใใ
ๅ3 ๆไธญใง "zoonosesโ ใจใฏไฝใ่ชฌๆใใใ
ๅ4 ไบบ้กใฎๆญดๅฒใฎไธญใงใ ็
ๆฐใฎไผๆใฎไปๆนใซๅคๅใใใใใใๆใ้่ฆใชใงใใใจ
ใฏไฝใใ
