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  • Macrophages, cytokines, t-cells...the immune system has a whole arsenal of ways to fight off an infection.

  • But when it comes to some diseases, the way the body defends itself can have unintended consequences.

  • In the case of pneumonia, the immune system's response can be lethal, earning it the nickname

  • the 'captain of the men of death.'

  • Pneumonia doesn't just refer to a single virus or bacteria.

  • It's a condition that can actually be caused by a number of different bacteria, viruses,

  • or even fungi, the most common being the bacteria streptococcus pneumoniae, who will be our main bad guy today.

  • So when we're talking about pneumonia, we're really referring to something that is happening to our lungs.

  • Hi, my name's Keith Klugman.

  • I'm the director of the pneumonia programs at the Bill & Melinda Gates Foundation.

  • I'm particularly fascinated by pneumonia and have been working to try and prevent pneumonia in poor children all of my life.

  • So pneumonia is an infection of the lungs and it is a very common infection.

  • The problem is that the lungs are thought to be fact the lungs aren't sterile.

  • But generally there's very few bugs in your lungs. The problem is that our

  • mouth and our nose are actually filled with bacteria and viruses and these can sometimes

  • get down into the lungs.

  • We're constantly being exposed to the bacteria and viruses that cause pneumonia like Streptococcus pneumoniae.

  • These pathogens can live in your upper respiratory tract without you even knowing it.

  • And that's because, for most people,

  • the immune system should be able to step in and stop them in their tracks, leading to immunity.

  • So you become immune to the bugs that you encounter when you're very young and by about

  • five years of age, you're pretty much immune.

  • But, for children under 5, the immune system is weaker, leaving the body susceptible to infection.

  • And it's not just children who are at risk.

  • Then, unfortunately, pneumonia risk comes back again in the elderly.

  • "Who is elderly?" you might say.

  • Generally defined as people older than the speaker.

  • So, for me, it's 65 and older

  • So pneumonia is a disease of the extremes of life, the very young and the very old.

  • Now, it's not only young children and older adults, anyone with a compromised immune system is at risk.

  • With the immune system unable to mount a defense in the respiratory tract, the bacteria are able to pass into the lungs.

  • Once there, the immune system will still try to defend the body.

  • But...

  • Unfortunately, they have a lot of side effects when this response occurs.

  • Macrophages first try to fight off the infection, but they can become overwhelmed, triggering the release of cytokines.

  • These cytokines lead to inflammation of the lungs, causing air sacs called alveoli to fill with fluid.

  • Yeah.

  • So alveoli are air sacs in the lungs that are where the exchange of oxygen and carbon dioxide take place.

  • And it's these alveoli that get filled with the fluid that's come from your bloodstream.

  • Now, there's no particular reason for red cells to get out of the bloodstream but white

  • cells that are included in the bloodstream are very potent cells able to kill bacteria

  • and they move in from the bloodstream out into the tissues at the site of infection.

  • But, filling the alveoli with fluid does more than just fight off the infection.

  • That's because, basically, your lung sacs are filling with pus.

  • The lungs are there and exquisitely designed for oxygen to pass from the air into your

  • bloodstream...And so unfortunately, instead of having nice, clear air pockets where this

  • exchange can take place, if they're filled with fluid, then the exchange of oxygen and

  • the release of carbon dioxide, which you breathe out, also is impaired.

  • This causes difficulty breathing as well as a whole host of symptoms that vary greatly in severity.

  • The effects of walking or atypical pneumonia can be so mild, someone might not know even know they have it.

  • In other cases, the infection can lead to death.

  • But, while pneumonia is still a disease that kills millions of people worldwide, there

  • isn't a good reason why it should still be so lethal.

  • The main driver of mortality from pneumonia, is access to treatment or lack thereof.

  • So, in fact, there are vaccines that work to protect from both bacterial and viral pneumonias.

  • In fact, the most successful vaccine for prevention of pneumonia is a bacterial vaccine.

  • So pneumonia deaths really shouldn't occur.

  • It's preventable, as I mentioned, by vaccines, also treatable by antibiotics.

  • Because of this, pneumonia deaths are much more common in poorer countries with fewer resources.

  • Which is why Dr. Klugman is working on ways to develop more effective treatments in these areas of the world.

  • But pneumonia deaths can still happen in places like the United States, especially if something

  • were to lead to people having compromised immune systems.

  • That could happen from contracting other illnesses, some of which are entirely preventable.

  • So, as you know, there have been outbreaks of measles recently in the United States.

  • And globally, measles has not been eradicated.

  • One of the major problems with measles is that it diminishes your immune response.

  • And kids who have measles can get bacterial and viral pneumonias after their measles so,

  • in fact, pneumonia is a major killer following measles exposure.

  • So a vaccine, there's a very potent vaccine for measles.

  • And measles prevention is a very important way of preventing deaths from pneumonia.

Macrophages, cytokines, t-cells...the immune system has a whole arsenal of ways to fight off an infection.

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Here's Why Pneumonia Is Still So Deadly

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    Jerry Liu posted on 2019/08/06
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