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People move. They always have; they always will.
Sometimes natural disasters, oppression, and wars drive
people to migrate. Nearly four million Iraqis, for example,
fled their homes between 2003 and 2007; half of them left
the country. At other times, people venture in search of
economic opportunity. Mexicans go to the United States,
Turks to Germany, and Indonesians to Malaysia.
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The number of international
migrants rose dramatically in recent decades.
Source:
United Nations |
Migration can occur within a country as well. After the U.S.
Civil War, countless African Americans moved north in search
of a better life. In modern China, about 100 million workers
have migrated to the economically prosperous provinces along
the coasts.
Human movement can have real benefits. People escape
desperate situations, find freedom, build new lives. And an
increasing number of people travel for business or fun. Half
a billion airline passengers cross international boundaries
each year. But migration and travel can also raise serious
health issues, because microbes and
pathogens can hitchhike
aboard unwary travelers. Migrants, moreover, often live in
crowded, unsanitary conditions where disease is rife.
(See
Health & You, below, for more information on migrants.)
PROBLEMS IN THE PAST
Diseases have traveled with humans throughout the ages. In
the 1300s, traders and travelers carried bubonic plague from
Asia to Europe. This deadly and highly infectious disease
swept through Europe, where it became known as the black
death. After the discovery of America, European explorers
and slave traders brought smallpox, measles, and other
illnesses to the New World. These diseases tore through the
Native American population, whose members lacked an immunity
to the Europeans' germs. In some places, they wiped out 80
to 90 percent of the land's original inhabitants.
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A 1937 mural in a U.S. government building depicts a tense
encounter with Native Americans over land. While weapons and combat received all the
attention, most Native Americans died from disease.
Source:
US Department of the Interior |
That grim fate befell indigenous peoples in other places
too. During the 1850s, measles killed a fifth of Hawaii's
people. Two decades later, the disease did the same thing in
Fiji. Between 1840 and 1860, influenza, measles, smallpox,
and whooping cough finished off 60 percent of the Maori, the
native people of New Zealand.
In the late 1800s and early 1900s, fear of disease underlay
many Americans' discomfort with the waves of immigrants
coming to the U.S. At Ellis Island, the immigration center
in New York Harbor, doctors examined thousands of newcomers
daily, keeping a sharp eye out for signs of typhus,
tuberculosis, and other
communicable diseases.
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In or about 1910, a doctor
examines immigrants at Ellis Island.
Source:
National Park Service |
NEW PRESSURES IN THE PRESENT
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Six hundred million people
travel by airplane each year.
Source: Varifrank |
If people have always spread diseases, what's the big deal
about globalization? The answer lies in the word
more. More
people are going more places than ever before. Air travel
has erased physical barriers—oceans, mountains, deserts—that
once kept diseases isolated longer. People are also moving
more quickly. That makes it far more likely a person
carrying germs will spread them long before he or she
becomes ill and is recognized as a threat to others' health.
Bleak statistics underscore the health impact of increased
mobility. Deaths from infectious diseases have doubled in
the U.S. since 1980. Most of those dying were migrants. That
doesn't surprise health experts, for migrants the world over
are at a higher risk of both contracting and passing on
infectious diseases. Migrants, for example, are five or six
times more likely to have tuberculosis than other people in
the same place.
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Good news: The number of tuberculosis cases in the U.S. has dropped, but may be leveling off.
Source:
Centers for Disease Control and Prevention |
Migrants' health problems are often compounded by dire
conditions. That likely happens when war, drought, or
disaster uproots large numbers of people. They crowd into a
new place, straining local resources. Food, water, and medical supplies become scarce, and sanitation rapidly
deteriorates.
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Makeshift conditions at a refugee camp in Zaire may allow disease to spread easily.
Source:
Centers for Disease Control and Prevention |
Under these circumstances, diseases like cholera can
suddenly erupt and move rapidly through a densely populated
area. This is especially true for people living in refugee
camps and relocation centers. Back in 1994, for instance,
epidemics killed 50,000 Rwandan
refugees during their first
month in refugee camps.
CASE STUDY: HIV-AIDS
Few diseases demonstrate the impact of human movement more
vividly than AIDS, which is caused by the
HIV virus. The
virus has probably existed among primates for hundreds or
even thousands of years in pockets of central African
jungle. Yet it only became a
pandemic in the past few
decades.
What happened? Humans probably contracted the virus by
butchering or eating infected non-human primates such as
chimpanzees and bonobos. Because humans are genetically very
similar to these animals, it would not have been a huge leap
for the HIV virus to successfully invade a human host. At
first, the infected people didn't travel much, so the
disease remained fairly localized. That changed after about
1950. Scientists are not entirely sure why, but it bears
noting that the second half of the 20th century was a time
of increased movement. Improvements in travel allowed more
people to visit Africa, and upheavals on the continent
created large groups of migrants and refugees.
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The number of people infected with HIV, the virus that causes AIDS,
continues to rise.
Source:
AVERT |
Due at least in part to increased mobility, the HIV virus
spread furiously, in Africa and around the world. In 2005,
three million people worldwide died of AIDS and another 40
million were living with the HIV infection. That's just one
example of what can happen when people move.
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The United Nations defines refugees as
“people who are outside their country and
cannot return owing to a well-founded fear
of persecution because of their race,
religion, nationality, political opinion, or
membership in a particular social group.”
They also count those “who have fled because
of war or civil conflict.”
