Download Disease and Death

Disease and
Death
SC/NATS 1510, Disease and Death
1
The Effect of Disease on Human
History
†
†
†
Epidemics and plagues wiped out vast
numbers of the population in a wide area.
Persistent infection in certain regions have
made human habitation impossible there.
Overall endemic low-level diseases
throughout human civilization have produced
low levels of health and shortened life
expectancy.
„
Often the result of inadequate diet.
SC/NATS 1510, Disease and Death
2
Hunting and Gathering Groups
†
†
Hunting and gathering ranged over a wide
range of food.
Malnutrition was rare.
„
„
Food consumption was as high if not higher than
the earliest agricultural groups.
Deficiency diseases would have been rare.
SC/NATS 1510, Disease and Death
3
1
Hunting and Gathering, 2
†
Modern hunting and gathering groups suffer
from intestinal parasites, such as worms.
„
„
These may have been common in prehistoric
groups, especially in Africa.
The spread of civilization out of Africa into
temperate climates would likely have reduced this
problem.
SC/NATS 1510, Disease and Death
4
Hunting and Gathering, 3
†
†
Death in childbirth and infant mortality would likely
have been high.
Probably no worse than early agricultural societies
or even early modern Europe.
„
†
In France, ¼ of all children died before their 1st birthday.
Life expectancy was short, though older people
would not have been unknown.
„
Among the San of Africa, about 1 in 10 are over 60.
SC/NATS 1510, Disease and Death
5
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.
„
This increased exposure to infectious disease.
SC/NATS 1510, Disease and Death
6
2
Relation of Animal and Human
Diseases
†
The domestication of animals exposed people
to diseases which affected animals.
„
†
†
In many cases domestic animals shared the same
living quarters.
Some animal diseases adapted to human hosts
and flourished unchanged.
Others altered their characteristics and
became human diseases.
SC/NATS 1510, Disease and Death
7
Relation of Animal and Human
Diseases, 2
†
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 hogs.
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.
SC/NATS 1510, Disease and Death
8
The Problem of Greater Concentration
of Population
†
†
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.
Few early societies kept human excrement out of
their drinking water.
„
„
„
Most used one watercourse for both purposes.
The mixture of water and human waste was a perfect
habitat for intestinal parasites such as worms.
Diseases such as cholera and dysentery were endemic.
SC/NATS 1510, Disease and Death
9
3
Infectious Diseases Require Crowding
Together
†
The steady rise in population and increasing density
allowed new diseases to become established.
„
†
Many infectious diseases (e.g., measles, mumps, and
smallpox) require a minimum number of human hosts to
survive.
Measles will die out on islands with a population of
less than ½ million.
„
„
The cities of Mesopotamia reached population levels this
high.
Other cities were close enough to make contact between
them frequent.
SC/NATS 1510, Disease and Death
10
Irrigation
†
†
Agriculture, as opposed to gathering naturally
growing wild crops, alters the environment in
was that encourage the spread of disease.
Agriculture required artificial irrigation.
„
The ditches that were dug held slow moving
water that provided prime breeding grounds for
parasites.
SC/NATS 1510, Disease and Death
11
Disease from Irrigation
†
†
†
Schistosomiasis, a blood fluke, causes extreme
debilitation and listlessness.
The blood fluke has an elaborate life cycle involving
both humans and water snails at different stages.
Irrigation ditches were ideal habitats for water snails.
People working in the ditches were exposed to
infection from the fluke.
SC/NATS 1510, Disease and Death
12
4
Schistosomiasis
†
†
The disease was
widespread in early
societies such as
Mesopotamia and Egypt
that depended on largescale irrigation.
Over 100 million people
suffer from schistosomiasis
infection today, many of
them in Africa.
SC/NATS 1510, Disease and Death
13
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.
SC/NATS 1510, Disease and Death
14
Malaria, 2
†
†
†
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.
SC/NATS 1510, Disease and Death
15
5
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.
„
†
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.
SC/NATS 1510, Disease and Death
16
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.
Most of the surviving records are not specific
enough to identify the diseases. (They were all called
“plagues.”)
„
„
Tuberculosis can be identified as early as 3000 BCE.
Most of the major epidemics are more likely to have been
more virulent forms of present day diseases such as
measles.
SC/NATS 1510, Disease and Death
17
Separate Developments in Widely
Spread Societies
†
The major areas of human population had little contact with
each other in the early phase of civilization. I.e.,
„
„
„
„
„
„
†
†
The Mediterranean
The Near East
India
China
The Americas
Oceania
Diseases established in one area were unknown in others.
Where a disease was established, the population had
developed a level of immunity.
When contact was established between societies, diseases
spread with lightning impact.
SC/NATS 1510, Disease and Death
18
6
Example: Smallpox
†
The Roman Empire
suffered a great “plague” in
165 CE, with death tolls of
around ¼ of the population.
„
†
And suffered further
outbreaks periodically over
the next five centuries.
The disease was probably
smallpox, which was new
to the Mediterranean area.
SC/NATS 1510, Disease and Death
Smallpox
19
Spread from India
†
†
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.
„
It was likely carried to the Mediterranean and to
China by traders who were themselves immune,
but who could transmit the disease.
SC/NATS 1510, Disease and Death
20
Leprosy
†
†
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.
SC/NATS 1510, Disease and Death
21
7
Leprosy, 2
†
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.
22
SC/NATS 1510, Disease and Death
Bubonic Plague
†
Another
epidemic
disease that
first appeared
in India was
bubonic
plague.
Pieter Bruegel, the Elder,
The Triumph of Death
SC/NATS 1510, Disease and Death
23
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.
SC/NATS 1510, Disease and Death
24
8
The return of the plague in the Middle
Ages
†
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.
SC/NATS 1510, Disease and Death
25
The Mongol Empire
†
The Mongol
empire that
came to
dominate Asia
in the Middle
Ages stretched
from European
Russia and the
Near East to
China.
SC/NATS 1510, Disease and Death
26
The Spread of the Plague along Trade
Routes
†
†
†
The Mongol Empire 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.
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.
SC/NATS 1510, Disease and Death
27
9
The Black
Death
28
SC/NATS 1510, Disease and 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.
29
SC/NATS 1510, Disease and Death
The Black Death, 2
There were two forms:
† The bacterial form
spread by fleabites
and killed in three or
four days.
† An even more virulent
pneumonic form
spread from person to
person could kill in a
few hours.
SC/NATS 1510, Disease and Death
Overall about 90% of
those infected died.
30
10
The Black Death, 3
†
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.
SC/NATS 1510, Disease and Death
31
The Black Death, 4
†
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.
After the first outbreak in 1346-1349 bubonic plague
reappeared at intervals for centuries.
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.
SC/NATS 1510, Disease and Death
32
The Black Death, 5
†
†
In the 17th century, 2 million people died of plague
in France.
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.
The plague began to die out in northwest Europe in
the late 17th century, but remained endemic in
eastern Europe and the Near East.
SC/NATS 1510, Disease and Death
33
11
Endemic Disease in the Americas
†
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.
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.
SC/NATS 1510, Disease and Death
34
Arrival of the Europeans
The Spanish conquistadors brought with them a wide range of
European diseases.
„
„
„
„
Smallpox, 1518-1526 – many millions died.
Measles, 1530-1531
Typhus, 1546
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.
† The effect was to completely destroy the flourishing Aztec
society.
SC/NATS 1510, Disease and Death
35
Process Repeated
†
†
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:
„
„
Malaria, early 17th century,
Yellow fever, 1648.
SC/NATS 1510, Disease and Death
36
12
And New Diseases for Europe
†
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.
SC/NATS 1510, Disease and Death
37
Syphilis
†
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.
SC/NATS 1510, Disease and Death
38
Other New Diseases
†
Typhus – Brought to western Europe from Cyprus by
Spanish soldiers in 1490.
„
„
†
Transmitted by lice. This was first discovered in 1910.
Delousing stations were set up during World War I.
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.
SC/NATS 1510, Disease and Death
39
13
Other New Diseases, 2
†
Cholera – 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.
It was only countered through improvements in sanitation
through the 19th century.
SC/NATS 1510, Disease and Death
40
Winning the Battle Against Infection
†
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 are killed by infectious
diseases.
SC/NATS 1510, Disease and Death
41
The Decline in Infectious Diseases
†
Factors in the decline of infection:
„
„
„
†
Some diseases have evolved into less virulent
forms.
Vaccines.
Antibiotics.
But these have all had a minor effect relative
to the overwhelming importance of:
„
„
Better diet.
Improved environmental conditions.
SC/NATS 1510, Disease and Death
42
14
Diet and Public Health
†
Diet
„
†
In the 19th century, the quantity and quality of food
available in the industrialized nations improved
significantly.
Public Health
„
„
„
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.
SC/NATS 1510, Disease and Death
43
The Battle Goes on 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.
„
Leads to widespread intestinal infections, especially in
children.
SC/NATS 1510, Disease and Death
44
Water Related Diseases in the Third
World
SC/NATS 1510, Disease and Death
45
15
Successes and Failures
†
Immunization programs:
„
„
Successful with smallpox.
Less successful with malaria.
†
Plague
†
Influenza
„
„
„
†
Controlled, but not eliminated.
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.
SC/NATS 1510, Disease and Death
46
Diseases of Affluence
†
†
The decline in infectious has been paralleled by the
rise of new diseases born of affluence.
Cancer
„
†
European cancer rates are 10 times higher than those in
West Africa.
Heart disease
„
„
Almost unknown 100 years ago except among the rich
who had a diet high in fat and sugar.
Now kills 40% of men and 20% of women in
industrialized countries.
SC/NATS 1510, Disease and Death
47
Reasons for the rise of diseases of
affluence
†
May be partly because people don’t die of
infectious disease and live long enough to get
cancer or heart disease.
„
†
We are healthy enough to fight off many
infections and sanitation has removed many
parasites that plague poorer societies.
But other reasons for cancer and heart disease
suggest themselves…
SC/NATS 1510, Disease and Death
48
16
Reasons for the rise of the diseases of
affluence
Change of diet in the wealthy nations.
† Reduction in fibre intake.
† Rise in sugar consumption.
† Higher levels of fat in the diet.
† Higher proportion of processed
foods.
SC/NATS 1510, Disease and Death
49
Reasons for the rise of the diseases of
affluence, 2
Intentional and non-intentional
intake of hazardous
chemicals.
† Tobacco use.
† Toxic chemicals in the
atmosphere, in water, and soil.
† Pesticides and herbicides.
† Food additives.
SC/NATS 1510, Disease and Death
50
17