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Viral and Fungal Causes of Pneumonia Video

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  • 0:41 What Is Pneumonia?
  • 1:45 Cause of Viral Pneumonia
  • 2:38 Causes of Fungal Pneumonia
  • 4:22 Signs and Symptoms
  • 5:55 Treatment Options
  • 6:28 Lesson Summary
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Instructor: Artem Cheprasov
This lesson will discuss two causes of pneumonia: viruses and fungi. We'll go over some of the main agents that cause these types of pneumonia and how viral and fungal pneumonia differ from bacterial pneumonia.

What Really Kills Us

Most of us spend our days worrying about the things in life that can hurt us from the outside. This includes cold weather, serial killers, lions, hurricanes, and so on.

Unfortunately, statistics show that something that kills us from the inside, like cancer, an endocrine disease (such as diabetes mellitus), or an infectious organism breaking down our body, is more likely going to be the cause of our eventual downfall.

Two groups of infectious organisms that can lead to our demise are viruses and fungi, and they can do this to us from a number of angles or organs that they can affect. Namely, for now, we'll talk about how they can affect the lungs.

What Is Pneumonia?

Bacteria, viruses, and fungi can all cause something known as pneumonia. Pneumonia refers to the inflammation of the alveoli in the lungs most notably as a result of a pathogenic infection. What I mean is, it's usually bugs that cause pneumonia, but do bear in mind that other things can cause pneumonia.

The alveoli referred to in the definition are the air sacs of the lungs. These are structures that help to exchange the gas entering and leaving our lungs. They're exactly like little balloons. They inflate as air comes into the lungs when you breathe in, and they deflate as you exhale.

Their inflammation and the inflammation of the rest of the airways as a result of disease can hurt the lungs and lead to fluid accumulation within the alveoli, making gas exchange quite inefficient.

While the most common cause of pneumonia - bacterial - is covered in another lesson, it's not unusual for viral pneumonia to actually predispose to a secondary bacterial infection. That's why it's important to discuss what causes this subtype of pneumonia.

Causes of Viral Pneumonia

Viral pneumonia is exactly what it sounds like. It's pneumonia caused by a virus. Some common viruses that cause this include:

  • The influenza virus, the one that causes the flu. These are the most common cause of viral pneumonia.
  • Respiratory syncytial virus, especially in children, but also adults.
  • Parainfluenza virus, again, especially in children and infants, but less so than respiratory syncytial virus.

To help remember that these guys cause viral pneumonia, just think about their names. You know for sure that the influenza virus causes respiratory signs because I'm more than sure you've had the flu. Well, 'parainfluenza' has the name 'influenza' in it, so that should be easy to remember. And respiratory syncytial virus (RSV) is a dead giveaway since it already has the word 'respiratory' in it.

Causes of Fungal Pneumonia

Fungal pneumonia also has a lot of possible causes, including:

  • Histoplasma
  • Coccidioides
  • Blastomyces
  • Aspergillus
  • Cryptococcus
  • Pneumocystis jiroveci pneumonia, the most common opportunistic infection in people with HIV

What I mean is that people who have a very weak immune system as a result of something like cancer or HIV/AIDS are more likely to be affected by this fungus. It's sort of a coward of a fungus. It doesn't hurt you unless you are already weak due to something else. It doesn't want to put up a fair fight and waits in the shadows to get you when you're down.

What's also interesting to note with respect to fungal pneumonia is that like pneumonia caused by bacteria, the fungi do not have to be inhaled to affect the lungs (although they most definitely can be). They can sometimes undergo hematogenous spread - that is to say via the bloodstream to the lungs from another place in the body that is affected by the fungus.

Just like you can use the airways to travel to a destination, so, too, can fungi use the air to travel into the lungs. But you can also get to your destination by using a network of roads. This network of roads within our body is our vasculature, which fungi and bacteria can use to get to your lungs from somewhere else.

Another cool tidbit is that certain fungi are more common in one place in the country versus another. Therefore, one type of fungal agent may be more likely to cause fungal pneumonia in the southwestern United States versus the Mississippi River Valley.

Telltale Signs on X-Rays

One important way to help differentiate bacterial pneumonia from viral and fungal pneumonia is via the use of X-rays. Bacterial pneumonia commonly causes something known as lobar pneumonia - that is to say only one lobe of the lung is affected. This is in contrast to fungal and viral pneumonia, both of which tend to make a diffuse interstitial pattern on the X-rays.

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