TOEFL Lecture 9 (Listen and Read)
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TOEFL Lecture 9
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As a part of our study of the effects of diseases on society,
of the, uh, social consequences of man's diseases,
we should certainly include yellow fever.
Now, yellow fever's a deadly disease that's caused by a virus,
and it's been the source of many epidemics since at least the eighteenth century
in Africa, Europe, and the Americas.
In fact, it still kills more than 30,000 people a year worldwide.
And there's still no cure for the disease.
However, there is a vaccine to immunize us against it.
The road to the discovery of that vaccine was a rocky one, I think.
It's called 'yellow' fever because one of its symptoms is jaundice -
a yellowish colour that the skin takes on, because of liver damage.
It's transmitted by mosquitoes, either from man to man - this's called the 'urban' cycle -
or from monkey to man - this's called the 'sylvatic' or 'jungle' cycle.
The disease probably originated in west Africa,
and it was carried from there to the West Indies
and the New World in the eighteenth century with the ships of the slave trade.
The first big outbreak of yellow fever happened in Cuba in 1762 and 1763,
and it killed thousands of American and British colonial troops there.
After that, between then and 1900,
it killed about ten percent of Cuba's population.
The next big epidemic hit in the heart of the United States,
in Philadelphia, Pennsylvania, in 1793.
It killed five thousand people there,
while twenty thousand more fled the city in panic.
These included President George Washington, Thomas Jefferson,
Alexander Hamilton, Dolly Madison,
and most of the federal government officials.
Because you might remember that Philadelphia was the capital of the United States then.
Washington, DC was still under construction,
and it would not be a working seat of government until 1800.
About twenty years after the Philadelphia epidemic,
another significant yellow fever epidemic hit Haiti.
In 1802, Napoleon Bonaparte had sent an expedition of 40,000 soldiers there
with the intention of using the island as a base for invading the United States, by way of New Orleans.
New Orleans was at that time still in the hands of France.
But Napoleon's army - including its commander, who was Napoleon's brother-in-law -
was completely decimated by the fever,
and his invasion plans were abandoned.
Later in the same century, in the 1880s,
France was again foiled, and history was again changed, by yellow fever.
The French effort to build the Panama Canal ended in failure
as a result of the heavy toll on the workers and technicians, from both yellow fever and malaria.
These epidemics continued to occur over and over
because no one had been able to figure out how the disease was transmitted,
how it was carried from person to person.
In Philadelphia, Benjamin Rush - who was a signer of the Declaration of Independence
and also the chief medical officer for the new government -
Doctor Rush relied so heavily on blood-letting as a treatment
that he probably killed more people than he cured.
The most widespread theory was that yellow fever spread through contaminated water
or by direct physical contact with infected people,
and some people actually abandoned family members in their panic.
The idea that mosquitos were the disease vector, the method of transmission,
had been proposed in 1881, by a Cuban scientist named Carlos Finlay,
but he hadn't been able to prove this to the satisfaction of other scientists.
It wasn't until twenty years later, in 1900, that Carlos Finlay's idea was finally proved.
The United States Army had occupied Cuba after the Spanish American War of 1898,
and since Cuba was still considered to be the breeding ground for yellow fever in the New World,
the US government commissioned a US Army surgeon, Doctor Walter Reed,
to solve the problem before its occupation forces also succumbed to this disease.
And Doctor Reed's team did soon prove that the mosquitoes were the culprits,
at their research center just outside Havana.
As a result, yellow fever was quickly eliminated from Cuba,
and the US Public Health Service started a mosquito control program
that included fumigation, eliminating or treating standing pools and bodies of water, and so forth.
In addition, the Panama Canal was completed by the Americans -
who then controlled the canal's operation for the next 99 years.
And Walter Reed - well, Walter Reed's name should be familiar to many of you.
The Walter Reed Army Medical Center in Washington, DC
is the well-known hospital where the US President, US congressmen,
and US military personnel receive medical treatment.