Download Disease and Death

The Effect of Disease on Human
History
Disease and
Death
1. Epidemics and plagues that wiped
out vast numbers of the population
in a wide area.
2. Persistent infection in certain
regions that have made human
habitation impossible there.
3. Overall endemic low-level diseases
throughout human civilization that
have produced low levels of health
and shortened life expectancy.
o Often the result of inadequate diet.
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Hunting and Gathering Groups
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Hunting and Gathering, 2
Hunting and gathering foods ranged
over a wide range of food.
Death in childbirth and infant mortality
would likely have been high.
• Malnutrition was rare.
• Probably no worse than early
agricultural societies or even early
modern Europe.
o Food consumption was as high if not
higher than the earliest agricultural
groups.
o Deficiency diseases would have been
rare.
• Modern hunting and gathering groups
suffer from intestinal parasites, such
as worms.
o In France, ¼ of all children died
before their 1st birthday.
Life expectancy was short, though older
people would not have been unknown.
o Among the bushmen of Africa, about
1 in 10 are over 60.
o These may have been common in
prehistoric groups, especially in
Africa.
o The spread out of Africa into
temperate climates would likely have
reduced this problem.
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Early Agricultural Societies
Agriculture exposed humans to a range
of diseases not previously encountered.
• Result was a major deterioration in
health.
• Settled societies meant that increasing
numbers of people were living in close
proximity to each other.
o This increased exposure to infectious
disease.
• The domestication of animals exposed
people to diseases which affected
animals.
o In many cases domestic animals
shared the same living quarters.
Relation of Animal and Human
Diseases
Some animal diseases adapted to
human hosts and flourished unchanged.
• Others altered their characteristics and
became human diseases.
• Many common human diseases are
close relatives of animal diseases.
Smallpox is similar to cowpox.
Measles is related to rinderpest and to
canine distemper.
Tuberculosis and diphtheria originated in
cattle.
Influenza is common to humans and hog.
The common cold came from the horse.
Leprosy came from water buffalo.
• Humans now share 65 diseases with
dogs, 50 with cattle, 46 with sheep and
goats, and 42 with pigs.
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The Problem of Greater
Concentration of Population
Infectious Diseases Require
Crowding Together
A large number of people living in cities
of several thousand or even villages of a
few hundred posed a major problem of
waste disposal.
The steady rise in population and
increasing density allowed new diseases
to become established.
• Few early societies kept human
excrement out of their drinking water.
o Most used one watercourse for both
purposes.
• Many infectious diseases (e.g.,
measles, mumps, and smallpox)
require a minimum number of human
hosts to survive.
• Measles dies out on islands with a
population of less than ½ million.
o The mixture of water and human
waste was a perfect habitat for
intestinal parasites such as worms.
• The cities of Mesopotamia reached
population levels this high.
o Diseases such as cholera and
dysentery were endemic.
o Other cities were close enough to
make contact between them
frequent.
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Irrigation
Schistosomiasis
Agriculture required artificial irrigation.
The ditches that were dug held slow
moving water that provided prime
breeding grounds for parasites.
Over 100 million people suffer from
schistosomiasis infection today, many of
them in Africa.
• Schistosomiasis, a blood fluke, causes
extreme debilitation and listlessness.
o The blood fluke has an elaborate life
cycle involving both humans and
water snails at different stages.
o Irrigation ditches were ideal habitats
for water snails. People working in
the ditches were exposed to
infection from the fluke.
• The disease was widespread in early
societies such as Mesopotamia and
Egypt that depended on large-scale
irrigation.
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Malaria
Forest clearance, by the swidden system
of slash and burn, created pools of
standing stagnant water that were
breeding grounds for mosquitoes.
• Mosquitoes carry malaria. When they
bite humans, malaria spreads.
In West Africa, malaria had been unknown
before agriculture became established. Now
it is endemic.
In China the spread of settlement
southwards from the Yellow River valley into
the wet rice-growing areas of the Yangtze
exposed the population to malaria and
schistosomiasis.
In India the spread of agriculture from the
Indus valley into the wetter and warmer
Ganges valley exposed settlers to a range of
new diseases, especially malaria.
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Disease Pattern of Settled
Societies
Diseases flourished in towns and cities,
because of lack of sanitation and
crowding.
• Until the 19th century in Europe and
North America, cities required a
constant influx of people to sustain
their numbers because of the high
death rates.
o , This is still the case in much of the
rest of the world
• At first new infections would cause
many deaths because there was no
acquired resistance in the human
population.
• Over time a degree of immunity would
develop.
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Low-level Endemic Disease plus
Periodic Epidemics
• A continuous low level of disease was
characteristic in ancient societies.
• This was interrupted by virulent
outbreaks killing large numbers in a
short period.
Separate Developments in Widely
Spread Societies
The major areas of human population
had little contact with each other in the
early phase of civilization.
Mediterranean
Near East
India
China
The Americas
Oceania
• Most of the surviving records are not
specific enough to identify the
diseases. (They were all called
“plagues.”)
Diseases established in one area were
unknown in others. Where established,
the population had developed a level of
immunity.
o Tuberculosis can be identified as
early as 3000 BCE.
o Most of the major epidemics are
more likely to have been more
virulent forms of present day
diseases such as measles.
When contact was established between
societies, diseases spread with lightning
impact.
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Example: Smallpox
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Spread from India
The disease was probably smallpox,
which was new to the Mediterranean
area.
• China had similar outbreaks in 161-162
and 310-312 CE, when death tolls
reached 40% in many places.
• Smallpox was known in India before
this time and the population there had
developed some immunity to it.
Smallpox
It was likely carried to the Mediterranean
and to China by traders who were
themselves immune, but who could
transmit the disease.
The Roman Empire suffered a great
“plague” in 165 CE, with death tolls of
around ¼ of the population.
o And further outbreaks periodically
over the next five centuries.
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Leprosy
Bubonic Plague
A similar disease to spread from India in
the 6th century was Leprosy.
• It became one of the major diseases
affecting the population of Europe.
In the 13th century there were 19,000 lazarets
(clinics) to accommodate and isolate
infected people.
The disease died out in Europe after the 14th
century. The population slowly built up
immunity.
Death rates fell as the disease became
endemic, but less virulent.
Pieter Bruegel, the Elder, The Triumph of Death
Another epidemic disease that first
appeared in India was bubonic plague.
It broke out in the Mediterranean in 542,
arriving by a ship from northeast India,
spread by fleas on black rats.
The population was vulnerable and the
death rate was high.
The disease arrived in China in 610, again
by boat from India, and killed about ¼ of the
population.
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The Spread of the Plague along
Trade Routes
The Mongol Empire
It opened up trade across the steppes of
Russia and the deserts of central Asia.
• The burrowing rodents of the area,
which were infected with bubonic
plague and carried infected fleas,
spread into China.
Better links for human contact and a larger
and more densely packed population made
the effect of the disease more catastrophic
when it returned in the Middle Ages.
The Mongol empire that came to dominate
Asia in the Middle Ages stretched from
European Russia and the Near East to
China.
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• Plague broke out in China in 1331 and
spread along the caravan routes to
reach the Crimea in 1346, and then to
the Mediterranean.
• It was spread further by ships carrying
black rats and infected fleas
throughout Europe, where it was
known as the Black Death
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The Black Death
The Black Death
The disease was
characterized by
buboes, which are
swellings of the
lymphatic glands, with
secondary swellings in
other parts of the body.
• The progress of the
disease:
Extreme pain, followed by
fever, vomiting, delirium,
and death.
The swellings, the excrement, vomit, blood,
everything in the infected person turned
black before death.
The spread of the Black Death across
Europe.
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The Black Death, 2
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The Black Death, 3
There were two forms:
• The bacterial form spread by fleabites
killed in three or four days.
• An even more virulent pneumonic form
spread from person to person could
kill in a few hours.
Overall about 90% of those infected
died.
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The Dance of Death. A popular theme in European
art and literature after the plague. This fresco from
the 15th century shows the grim reaper dancing in
turn with all the members of the society, showing no
favourites.
In total about 1/3 of the population of
Europe died in the initial outbreak.
• Many tried to flee, thereby helping to
spread the disease across the
countryside.
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The Black Death, 4
Endemic Disease in the Americas
After the first outbreak in 1346-1349
bubonic plague reappeared at intervals
for centuries.
o Between 1347 and 1536 there was a
major outbreak somewhere in
Europe on average every 11 years. In
the period from 1536 to 1670 it
averaged once in 15 years.
o In the 17th century, 2 million people
died of plague in France.
o The Great Plague in London in 1665
was brought from Amsterdam and
spread across the city. About 6000
people a week were dying of the
disease in London.
It is likely that the urban areas in the
Americas – the Aztec and Incan empires,
for example – had crowded and
unsanitary conditions producing
intestinal parasites and dysentery
similar to the Old World.
• It is certain that the major endemic
diseases of Eurasia had not spread to
the New World.
o The lack of domesticated animals in
the Americas meant that diseases
did not spread from animals to
humans there as they did on other
continents.
The plague began to die out in northwest
Europe in the late 17th century, but remained
endemic in eastern Europe and the Near
East.
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Arrival of the Europeans
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Process Repeated
The Spanish conquistadors brought with
them a wide range of European
diseases.
o Smallpox, 1518-1526 – many millions
died.
o Measles, 1530-1531
o Typhus, 1546
Similar collapses occurred throughout
the Americas from Peru to Canada as
European diseases spread through the
New World.
• The process was repeated in the next
centuries by the arrival of slaves from
Africa bearing more diseases endemic
to their society. Examples:
o Malaria, early 17th century,
o Influenza, 1558-1559
• Estimated casualties: In central
Mexico, the centre of the Aztec empire,
the population fell from 25 million
before the conquest to 1 million in
1600.
o Yellow fever, 1648.
• The effect was to completely destroy
the flourishing Aztec society.
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And New Diseases for Europe
Other New Diseases
Syphilis was a disease not known in
Europe before the 1490s.
It was noted during the French army
invasion of Italy in 1494.
It then reached India in 1498 with the sailors
on Vasco da Gama’s voyage.
By 1505 it had reached China and Japan.
• Did it originate in the Americas?
In the 15th century, people were convinced
that syphilis originated in the Americas and
was brought back by the sailors from the
first expeditions.
The first recorded appearance was in
Barcelona in 1493, a year after Columbus’
first voyage to the Americas.
There is controversy over this. Another view
is that it was a form of the disease yaws
already endemic in Europe.
• Typhus – Brought to western Europe
from Cyprus by Spanish soldiers in
1490.
o Transmitted by lice. This was first
discovered in 1910. Delousing
stations were set up during World
War I.
o Armies and navies were among the
main mechanisms for the spread of
new disease. They lived in primitive
conditions of overcrowding and poor
sanitation, and traveled to and from
new locations.
• Until the 20th century, armies nearly
always lost more soldiers to disease
than to battle.
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Winning the Battle Against
Infection
Other New Diseases
Cholera
o Transmitted through drinking water
polluted with human wastes.
Was endemic in Bengal and had spread to
adjacent areas.
In 1817 British troops carried it from Calcutta
to the north of India.
It spread to southeast Asia and then to East
Africa in 1821.
In 1826, it infected the Russian army. By
1831 it reached the Baltic.
From there to western Europe, the United
States and Mexico.
Caused panic in Europe where primitive
water supply and sanitation systems allowed
the disease to spread rapidly.
The pattern that has existed throughout
human history has been broken in the
last 200 years in the industrialized
nations.
• Life expectancy has increased
dramatically.
• Infant mortality has all but disappeared
in the developed nations, except for
those with inherited or incurable
diseases.
Reason: Fewer killed by infectious
diseases.
It was only countered through
improvements in sanitation through the 19th
century.
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The Decline in Infectious Diseases
Factors in the decline of infection:
Diet and Public Health
Diet
1.
Some diseases have evolved into
less virulent forms.
2.
Vaccines.
• In the 19th century, the quantity and
quality of food available in the
industrialized nations improved
significantly.
3.
Antibiotics.
Public Health
But these have all had a minor effect relative
to the overwhelming importance of:
4. Better diet.
5. Improved environmental conditions.
• Effective sewers and treated drinking
water reduced water borne diseases
such as cholera.
• Better Housing, which reduced
overcrowding, damp, and poor
ventilation.
• Prevention of food contamination:
Pasteurization of milk, canning, and
refrigeration.
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The Battle Goes on in the Third
World
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Water Related Diseases in the
Third World
The main causes of disease are still
widespread in the Third World.
• The patterns of disease that affected
the entire world for thousands of years
are still prevalent outside of the
industrialized nations.
• Diet: Chronic malnutrition or starvation
still common.
• Public Health: Sanitation conditions
still poor in many parts of the world.
Especially contaminated water.
o Leads to widespread intestinal
infections, especially in children.
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Successes and Failures
Diseases of Affluence
• Immunization programs:
The decline in infectious has been
paralleled by the rise of new diseases
born of affluence.
Successful with smallpox.
Less successful with malaria.
May be partly because people don’t die of
infectious disease and live long enough to
get cancer or heart disease.
• Plague
Controlled, but not eliminated.
• Influenza
• Cancer
Virulent strains still appearing.
The 1918 outbreak swept the entire world,
resulting in 15-20 million deaths. (Especially
in Europe where people had been
weakened by poor diet due to World War I.)
• Aids
First recognized in 1980s. May have
crossed from monkeys. No vaccine
available.
Infection rates rising rapidly, especially in
Africa.
o European cancer rates are 10 times
higher than those in West Africa.
• Heart disease
o Almost unknown 100 years ago
except among the rich who had a
diet high in fat and sugar.
o Now kills 40% of men and 20% of
women in industrialized countries.
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Reasons for the Rise
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Reasons for the Rise
• Change of diet in the wealthy nations.
o Reduction in fibre intake.
o Rise in sugar consumption.
• Intentional and non-intentional intake
of hazardous chemicals.
o Tobacco use.
o Higher levels of fat in the diet.
o Toxic chemicals in the atmosphere, in
water, and soil.
o Higher proportion of processed
foods.
o Pesticides and herbicides.
o Food additives.
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