So pandemic, this course
is all about pandemics, right?
Pandemic again is an epidemic that has
spread over several countries or continents
and usually affecting a large number of people.
This is a soft qualitative
definition but we attempt to,
tend to make it a little more
solid for administrative purposes.
So here's some notable pandemics of
the modern era going backwards in time.
Of course right now, the pandemic
on everyone's mind is COVID-19.
And it started in late 2019 when the
first cases were detected in Wuhan, China.
It's caused by the Coronavirus SARS-Cov2.
And as of the making of this video,
it's killed over a million people worldwide
and infected over 55 million people.
Of course the HIV/AIDS pandemic is still with us.
It's peak years though were
between 2005 and 2012.
After that, effective treatments and
control mechanisms were put into place,
but it's still affecting many people.
And you probably know it's
caused by the HIV retroviruses
and it's killed over 36 million people to date.
Before that we have the
various influenza pandemics.
In fact, prior to COVID-19,
the last pandemic to be declared
by the WHO was the 2009 influenza pandemic.
In 1968, we had a very large H2N2 Influenza A
pandemic that killed a million people.
And in 1956, the Asian flu killed a million people
1889, H2N2 once again killed a million people.
But the big influenza pandemic we always
talk about is the spanish flu of 1918 to 1920.
That was the H1N1 subtype that killed
anywhere from 50 to 100 million people.
In fact, some people believe it killed
so many soldiers during World War I
that it was probably a contributing
factor to the ending of World War I
having taken so many people off the battlefield.
Today, many of the H1N1 strains floating
around are descendants from this flu.
So these diseases never fully leave
us unless they are fully eradicated.
There's always some genetic semblance
of them floating about in their descendants.
Going further back in time, we can talk
about the many worldwide cholera pandemics,
including one that's going on today
and it's resulted in millions of deaths.
But it also was the foundation
of modern epidemiology.
In the mid to late 1800s, Jon Snow in
England was investigating a cholera outbreak
and he didn't know anything about pathogens
or what caused diseases but he was able to count
And he looked at a neighborhood in
London where cholera cases were happening
and managed to trace them back to a
single water source, the broad street pump.
This was a medical mystery and he solved
this medical mystery using detective work
and in doing so invented a
whole new science, epidemiology
which essentially is medicine using numbers.
And using numbers, he figured
out that this one pumping station
was the source of much of the
infections of cholera in that neighborhood.
Maybe you can figure out if that's a common
source, point source, propagated type of epidemic.
Of course, you can't talk about pandemics
without talking about various plagues:
the plague of London, the black plague,
the great plague through the Middle Ages.
And up to the 17th century, there are 40
outbreaks during that period killed
that might have up to 20%
of the human populaiton.
20%, that's extraordinary.
Smallpox is one of the great plagues
of humankind and of course famously,
is a disease that we eradicated
using vaccines and clever epidemiology.
Smallpox probably killed around 10 million
people and wiped out Native Americans.
In fact, we think that when
Europeans arrived in the new world,
it wasn't so much conquistadors
killing people that did most of the damage,
it was the diseases they
brought most notably, smallpox.
The black death of the 1400s
killed perhaps 200 million people.
In fact, in Venice around that time, they
invented the first formal system of quarantine.
Remember they didn't know
what was causing the disease.
They didn't know about bacteria or pathogens,
but they figured out that if infected people
were kept away from everybody else, quarantined,
they were less likely to propagate the disease.
And that's an important
discovery that we still use today.
In fact, despite being in the 21st century, many of
the techniques we use to control COVID-19 today
are based on 19th century efforts and earlier.
One of the earliest known
pandemics, the 'Plague of Justinian',
named for the emperor of Byzantium
of that time, and that was also
the bubonic plague and probably
killed between 30 and 50 million people.