Polio: Causes, Symptoms, and Treatments

Polio: Causes, Symptoms, and Treatments
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  • 0:08 An Ancient and Modern Disease
  • 0:59 What is Polio?
  • 2:18 Why Does Polio Occur?
  • 5:25 Clinical Signs,…
  • 6:34 Treatment and Prevention
  • 7:10 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov
This lesson will describe a crippling disease known as polio. We will discuss its history, signs, symptoms, treatment, prevention strategies, who is most likely to get this disease and why this may be the case.

An Ancient and Modern Disease

A lot of movies and even documentaries like to glorify the history of many places and times. When I say ancient Egypt, you think of the beautiful Cleopatra or the boy-king Tutankhamen. When I say the Middle Ages, you think of Sir Lancelot, and when I say modern Africa, you think deserts or lions.

But the overarching theme of all of these places and times is far less satisfying and far uglier. Wars, famines, and city streets filled with diseased people left and right was more of the norm.

One disease that has been around for thousands of years, including modern times, has affected some of the most famous people in the world, such as Franklin D. Roosevelt, and is very crippling.

What Is Polio?

This disease is known as polio. Polio is a contagious, virally induced disease that can cause paralysis and death. The more technical name for polio is poliomyelitis.

The reason it is called poliomyelitis is because the prefix polio means 'grey' in ancient Greek, myelo refers to the spinal cord, and itis refers to the inflammation of something. Therefore, when we combine all of these terms together we get the inflammation of the spinal cord's grey matter, or poliomyelitis.

This disease typically affects children under five years of age and, in 1 of 200 infections, it will lead a person to develop irreversible paralysis. In 5%-10% of these cases, this irreversible paralysis may actually affect muscles involved in respiration, or breathing, leading to an individual's death when they can no longer breathe.

While this was a historically prevalent disease resulting in hundreds of thousands of people being affected all around the world, it is now mainly localized to a handful of countries, such as Afghanistan, Nigeria, and Pakistan, and only affects a few hundred people per year.

Why Does Polio Occur?

The reason this disease even occurs is as follows.

First of all, the virus responsible for causing polio is unsurprisingly known as the poliovirus. This virus is spread from person to person via the horizontal transmission route, such as when someone contacts a sick person, is around someone who sneezes or coughs out this virus from their throat, drinks water contaminated with a sick person's feces, or eats food that has the virus on it. Therefore, in places where sanitation is very lax, like poor rural areas, this disease is much more likely to spread than in modern cities.

Once the virus enters a person's body it establishes itself in the cells of the intestinal tract. It eventually multiplies in the lymphoid tissue of the intestinal tract and the throat, such as your tonsils. From there, the virus moves into the blood, and from there will move into the central nervous system, including the spinal cord, and sometimes the brain. If it causes disease in the brain, we term this polioencephalitis, with encephalo referring to the brain.

You can liken the way this virus multiplies to how a virus that affects computers may multiply and spread. It's done in several stages. First, a virus enters one computer, where it hijacks the machinery there to replicate itself. This is the stage of replication in the lymphoid tissue in our body. Then the computer virus uses your email to spread along the World Wide Web's network of communication channels.

This is like the stage when the virus uses your network of blood vessels to spread around the body. Then, the computer virus reaches its final destination, your computer's processor, the control center of your computer, which is like your central nervous system. This includes the brain and spinal cord.

Once the poliovirus reaches the spinal cord it will target motor neurons located there. These motor neurons are the nervous system's cells involved in moving your body around. This targeting will result in the motor neuron's injury or death. If the motor neuron is injured or dies, then the nervous system cannot signal your muscles to move. If the muscles can't move, neither can you. This is what we call paralysis. The motor neurons are just that, they're like a car's motors that turn the car's wheels. If the motor fails, the wheels can't turn and the car can't move. If the motor neuron fails, the legs can't move, and the person is paralyzed.

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