Hi, I’m the History Guy. I have a degree in history and I love history,
and if you love history too, this is the channel for you.
We're in the midst of a particularly severe flu season, with higher than
average infection rates. And as the Centers for Disease Control have said,
now we are seeing a disturbing trend where there's been an increase in reports of flu-like symptoms,
which indicates that there might be an increase in infections, even though we thought we'd already
hit the peak of the 2017-2018 season. And while that is reason for concern, and certainly reason
to make sure that you get your flu shot, and that you wash your hands regularly, still doctors are
only describing this season as being moderately severe. And moderately severe is really nothing
compared to what happened a hundred years ago, when the world faced the most severe influenza
outbreak in human history. A story whose memory seems to have faded a bit in the modern world.
The influenza pandemic in 1918 and 1919 was the deadliest flu outbreak in human history,
second only to the Black Plague, for the deadliest epidemic of disease in human history. It infected
as much as half of the world's population, with at least a quarter of the population showing
clinical symptoms. It killed nearly 20% of those, or roughly five percent of the entire population
on earth at the time; between fifty and a hundred million people. Worst, unlike most flu outbreaks,
it disproportionately killed young, and healthy people. So much so that in the United States,
deaths due to the pandemic decreased the average life expectancy in the nation,
by 12 years. Described as the greatest medical Holocaust in history, it hit fast,
killing 25 million people in the first 25 weeks of the outbreak. At its peak,
deaths in the hospital exceeded 25% per night. It is sometimes called the Spanish Influenza,
but that is a misnomer. The disease did not start in Spain. Rather, because it occurred during the
First World War, most nations censored the news of the outbreak, afraid that it would
affect national morale. But because Spain was neutral, newspapers were able to report on it
freely there, giving the false impression that the pandemic was centered in Spain.
To understand the great pandemic, it is important to understand what influenza is. Influenza,
or the flu, is an infectious disease caused by the influenza virus. The most
common symptoms include a high fever, runny nose, sore throat, muscle pains, headache,
coughing, and feeling tired. It can be mild to severe. It is contracted by direct contact with
an infected individual, or the droplets that are expelled, through coughing and sneezing,
can also be transmitted by touching surfaces that have been contaminated by the virus.
Three types of influenza commonly affect humans, influenza A, B, and C.
Influenza B mutates relatively slowly, and that means that most people will develop some
immunity by an early age. That means that Influenza B outbreaks are relatively rare,
and do not cause pandemics, that is an epidemic large enough, to say, cover an entire country, or
maybe even the entire world. Influenza C is also very rare, and usually only causes mild symptoms.
The real risk is Influenza A, which is the cause of most human influenza,
and all human influenza pandemics. The outbreaks, popularly called the Spanish flu, the Bird Flu,
the Asian Flu, and the Hong Kong Flu, were all versions of Influenza A. While the natural hosts
of Influenza A are wild bird populations, the flu sometimes transmitted to domestic fowl,
like domestic ducks, or chickens, and then can, although rarely, pass to humans. Pigs are also
vulnerable to many types of influenza. Pigs can be affected by Influenza C, but the term Swine
Flu almost always refers to some type of Influenza A. Although influenza is common in pigs, it is not
common for pigs to pass influenza to humans, and even then, rarely does it lead to human influenza.
Only 50 cases of direct transmission from pigs to humans have been reported since 1958. You cannot
get influenza from the meat of an infected pig if the meat has been properly cooked.
Influenza A has two types of glycoproteins. As those two glycoproteins affect how the disease
is transmitted and replicated, variations in their indigents affect your immunity to
the strain. Thus, variances in the H and N glycoproteins, in influenza A strains,
are referred to by H and N types. The 1918 outbreak was the H1N1 virus,
whereas the Bird Flu pandemic in 2006, was the H5N1 strain.
The real risk of Influenza A is that it mutates rather quickly, and thus has a greater chance of
producing a strain that is less affected by previously gained immunity. As it can
grow in people, and birds, and pigs, then it has multiple places where a novel strain can
arise. That might be because it is less affected by previously gained immunity, more virulent.
As flu vaccines take a great deal of time to incubate, they depend upon a
best guess of how the virus will mutate in the meantime, and so may be more or less effective
in a given year at providing immunity to the illness. We generally think of winter months,
roughly October to April, as flu season. While flu is ever-present in the population,
there appears to be more opportunity for transmission in winter. There are a few
theories for why flu is more common in winter, first flu viruses seem to adapt to the cold,
possibly by creating a protective shell that then allows them greater ability to survive
for transmission. Second, in warm months, humid air pulls the airborne virus down,
making it less likely to be transmitted. And finally, humans see less sunlight,
and therefore, have lower vitamin D levels in winter, so their immune system may be repressed.
But a new strain can arise at any time, and epidemics, and pandemics, can and have occurred
outside of the winter months. And that in fact happened, in 1918. The first apparent cases
occurred in North America in March of 1918. It was then contracted by young men from America heading
to the First World War, and spent with them to France, where it quickly spread throughout Europe,
then Africa, and Asia. But this first wave, from March to July, was not that exceptional. While it
had high infection rates, its mortality rate was not unusual. But then the virus took a turn. In
August, flu broke out on a British ship heading to Sierra Leone, quickly the outbreak spread,
from the crew, to the dockworkers, to the rest of the country. But it was different, the death
rate for those infected was more than ten times what had been seen earlier in the year. That more
virulent strain reached the port of Brest France, an important port serving the needs of the war,
and so spread throughout Europe. The much more deadly strain apparently was spread to America
through the port in Boston, where it spread across the country, killing more than 600,000
people. It was the second deadliest event in American history, only behind the Civil War.
By October it reached India, where it killed as many as seven million people. The outbreak was
particularly deadly among populations in the Pacific Islands, and Alaska, where it killed
as much as 25% of the population, leaving whole villages abandoned. The 1918 strain was around
20 times deadlier than a normal flu strain. As a complicating factor, in 2008 researchers found
that the strain weakens the bronchial tubes, which then makes the victim more susceptible
to an often fatal secondary bacterial infection of pneumonia, The pandemic was particularly
terrifying because it killed a disproportionate number of people in their prime, typically,
flu pandemics follow a U-Curve, affecting mostly the very young and the very old, who are more
vulnerable. But the 1918 epidemic followed a W, with a spike in deaths in the middle. Young
healthy people between 20 and 40 years old. A population usually able to withstand influenza.
Overall, nearly half of the deaths in the 1918, 1919 flu pandemic, were young adults
between the age of 20 and 40 years old. That is a phenomenon that was unique to that pandemic year.
One reason was because the virus caused something called a cytokine cascade. When a person gets an
infection, cytokines signal and activate immune cells, which then stimulate more cytokines. The
body usually regulates this feedback loop, but for reasons that are not well understood, the loop can
keep building during some severe infections. This can be especially deadly with the flu, since the
infections in the lungs, where the person can literally drown in their own white blood cells.
Because this is an overreaction of the immune system, a strong healthy immune system might
have actually been a deadly disadvantage. Further research however, suggests that it was cultural
conditions at the time that made the pandemic so deadly. Conditions at army camps for example,
group people up, making the spread of the disease easier. International travel was further impacted
by the war, allowing the disease to spread more quickly around the globe. At the same time,
many communities had a shortage of physicians as so many were part of the war effort,
and many soldiers died of influenza because their lungs had been weakened by the poison gas used
in the war. Another possible explanation for the high death rates was put forward
by researchers in 2009. Some of the deaths may have been due to aspirin poisoning. Unaware of
the risks of aspirin poisoning, doctors at the time recommended extremely high doses to treat
the fever. And a review of symptoms suggest that that may have killed thousands of people.
Perhaps the most disturbing part of the 1918, 1919 influenza pandemic, is how little we still
know about it, even a hundred years later. As researchers have never been able to isolate the
virus strain from the original outbreak, between March and July, no one has been able to come
up for an explanation for how it became so much more deadly, in such a short period of time. As
it spread in so many places, no one has been able to even identify where the origin of the outbreak
was. Researchers do agree that both humans, and pigs, who also had an outbreak at the same time,
had almost no immunity to the strain, suggesting it was brand-new. And while the research,
and genetics indicate that it was an avian flu, no one's been able to determine the
point at which it jumped from birds to humans. In short, we really don't know how such a deadly
strain arose so quickly. And if your question is, “Could it happen again?”, it already has.
While the H1N1 strain seemed to disappear from the human population in the 1950s after the
rise of the H2N2 strain, it reemerged in 1977. Genetic research indicated that the 1977 strain
was almost certainly a pre-1950 strain that had to have escaped from a laboratory. And in 2009,
a global pandemic, that killed worldwide as many as around a half million people, was the H1N1
influenza virus. And new outbreaks occurred in Myanmar and the Maldives just last year in 2017.
And while we have much better techniques for treating the flu, and managing pandemics,
a 2006 study by the US Armed Forces Institute of Pathology concluded, that despite today's
modern antivirals, antibiotics, immunizations, and prevention techniques, if a strain were to
arise today that was as virulent as the 1918 strain, it would likely kill more
than a hundred million people. The US Centers for Disease Control offer you three pieces of
advice to help protect yourself from the flu. Number one, get your flu shot. Number two,
take normal precautions, like washing your hands, wiping down surfaces, and staying home
if you're sick. And number three, if your doctor prescribes you antiviral medications, take them.
I'm the History Guy, and I hope you enjoyed this edition of my series, five minutes of history,
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