Hello, Steve here. Today I am moving over
as the voice of kurzgesagt for something really special. Our dearest friend John Green
would like to tell you a story that's very close to his heart. So, let's hear it
from him directly. Hey, John! Hey, Steve. Thanks so much! Lets dive right in: The white death has haunted humanity like
no other disease following us for thousands, maybe millions of years. It
was there when we tamed fire, invented culture, and ventured out of Africa
to conquer the world. In 1815 it caused one in four deaths in Britain. In the last
200 years it killed a billion people, way more than all wars and natural disasters
combined. Even today it’s the infectious disease with the highest kill count. But… Do you even
know what we are talking about? We’re talking about Mycobacterium tuberculosis, which causes
tuberculosis or TB – our original arch enemy. Right now one in four humans alive are infected
with the bacterium – you may be one of them. So how is it possible that
we never hear about TB? Well, the White Death is the perfect human
predator: Very infectious but very quiet most of the time, careful not to murder
recklessly. Perfectly adapted to your immune system and just physically incredibly hard
to kill. What exactly makes it so powerful? The Perfect Human Predator Usually the bacterium enters your body through
the airways and sets up home in the lungs, a giant living cave system, defended by billions
of macrophages, powerful guard cells that hunt and kill intruders. The TB bug is quickly
attacked and devoured alive. Unfortunately this is its plan. The white death is the worst
kind of parasite – an immune system parasite. Macrophages grab their victims,
trap them inside a phagosome and flood it with acid that rips them to pieces.
But TB evolved a thick, waxy coat that makes it completely immune to those acids. Worse,
it captures and modifies the macrophage to be a perfect host. Like a tiny vampire, the
parasite slowly consumes the cell. TB then replicates extremely slowly. Other microbes that
make you sick multiply up to 60 times faster, exploding their numbers before the immune
system can eradicate them. But the white death is so well adapted to you, it has already
won by being here. No need to rush things. When its host cell is sucked dry and dies, the bacteria infect new macrophages.
Although these bacteria are stealthy, the decaying corpses they leave behind do
activate a proper immune response – your body knows something is up and mobilizes its
forces. But once again, this is part of the plan. Macrophages and many other immune cells
try to kill the bacteria, but that thick cell wall makes them a formidable fortress and
resistant to many attacks. And it infects its attackers in the process. So when your cells
can’t kill them they do the next best thing: keep the parasites from escaping. A granuloma is
formed, a sort of white blob. In the center is a core of infected and dead macrophages – a pleasant
home and food for the bacterium. Other immune cells surround this sphere of death to contain it
– creating a safespace where TB can sit for years. Worse, it is perfectly protected from medication
and releases chemicals that make it hard for your heavy immune weapons to be activated. This
is the stalemate version of Tuberculosis. The infection is sleeping and the bacteria is
doing its thing. This is going on right now in up to two billion people! But in one in ten
of them, the disease will become active. Active Tuberculosis is an emergency. But again, a
slow one. If your immune system can’t contain the infection anymore, granulomas burst. Suddenly
your lungs are filled with macrophage corpses and fresh bacteria. Your immune system panics
and overreacts. Hordes of soldiers leave your blood and rush to the infected areas. They
order inflammation and fluids flood into your lungs. But unfortunately, your lungs are
not made to be a battlefield. In their panic, your immune cells don’t care – they’re
running around with flamethrowers, trying to purge the infection
but causing terrible damage. As fluids and dead tissue amass, it becomes
difficult to breathe and you begin coughing hard, sometimes even coughing up blood. And
again this is part of the plan because now you spread millions of bacteria
catching rides in tiny droplets. You burn a high fever and lose weight
as your body is severely stressed. You turn into a ghost version of yourself.
Even if you are treated, this phase can last weeks to months and is very serious.
Insufficiently treated, TB will over months, years, or even decades slowly overtake your body.
Especially for children or those already weakened, this can be too much and the disease wins the
war. The bacterium spreads to other organs, lung function breaks down and the patient dies.
1.3 million people died this way in 2023 alone. The Worst Kind of Problem Tuberculosis is the worst kind of
problem: A slow one. Instead of killing millions quickly like Covid, scaring a
panicked humanity into frantic action, TB is a smoldering fire. Killing too
slowly for our short attention span. The symptoms are often mild for many months, so
you don’t feel in danger. Tuberculosis doesn’t want to kill you of course, it wants to
stay alive and spread. And to do this, it exploits human behavior: The people you are
most likely to infect are your family and friends, coworkers or neighbors, the people you spend a lot
of time with. When Covid brought the world to a halt, the average patient infected 2-3 people. An
active TB patient infects 5 -15 people in a year. Most people catch it via breathing
in tiny droplets from a cough or sneeze. This is especially common in crowded, poorly ventilated housing or workplaces.
Which is why TB exploded during the Industrial Revolution. And indeed wherever we
see new unplanned and overcrowded urbanization, from Lagos to St. Petersburg, we tend to
see a rise of the White Death alongside it. Today most cases of active Tuberculosis
– the version that spreads the disease further – can be cured with a four-month
regimen of four different antibiotics. But if that’s the case… How is this still the
deadliest infectious disease on earth? Between 1940 and 1965, humans developed several
drugs to fight TB, finally making it curable. It was a true achievement of human ingenuity.
But we didn’t do a great job of distributing the cure. While Tuberculosis is almost extinct
in much of Europe, the US and the Middle East, it is still a very real threat in most of the
world. TB kills people primarily in Africa, South America and Asia. In 2022 two thirds
of all TB cases were in just six countries: India, China, Indonesia, the Philippines,
Pakistan and Nigeria. Almost half of all Tuberculosis deaths happened in South East Asia. But as it is a slow problem like climate change,
it was ignored instead of fought aggressively, which enabled more and more strains of
TB to develop antibiotic resistance. Which is a problem because we
kinda stopped making new drugs. In the first twentyfive years of the
antibiotic era, we developed eight different classes of drugs to treat TB. And
then, in the 47 years between 1965 and 2012, we developed none. Developing new drugs
is extremely expensive and there was no concentrated effort to eradicate TB,
and there simply wasn’t enough profit incentive. There is a vaccine, but it’s over
100 years old and not particularly effective. But beginning in 2012, we did finally develop
two new classes of drugs that treat TB, and we may finally be at an inflection
point again, as better vaccines are on the horizon. Companies that made Covid tests
also developed a quick test for TB. So, we now have a real opportunity to push
this disease back until it dies forever. But only if we get enough people to know about
TB – like you do now – and to care about it. A century ago in the United States, there were
almost as many hospital beds for TB patients as for treating all other illnesses and injuries
combined. The White Death was a leading cause of death in the US and then one day it just
wasn’t anymore. And we can do this again. 4,000 people died of tuberculosis yesterday,
and we simply don’t have to accept a world where so many of us still die of a disease
we know how to cure. The White Death has been with us for millions of years. It is
time to continue our journey without it. If you want to learn more about
tuberculosis and the folks working to fight it through clinical trials and care
delivery and also learn how you can help, check out the organization Partners in Health
at pih.org/programs/tuberculosis. We’ve put a link in the description for you. Also, if
this wasn’t enough TB for you, there’s a Crash Course Lecture on the history and presence
of TB. We’ll include a link to that as well. Steve, I'll see you on Fri....no! This isn't
Vlogbrothers...soon. I'll see you soon, Steve.
