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.
Furthermore, if a person's leg is paralyzed, the body has no use for the muscles involved in locomotion. Since there's no use for these muscles, they deflate. Think of it like this: people who want to inflate or increase the size of their muscles work out a lot. Well, if you stop working out then those muscles will get smaller. If you stop moving them altogether they will get even smaller. This is called muscle atrophy and is a common sign in people who are affected with paralytic polio.
Clinical Signs, Symptoms, and Diagnostics
While more than 90% of people who are infected with polio experience no symptoms at all, the unlucky few that get affected by this virus experience a wide range of problems, ranging from:
- The paralysis I just mentioned
- Meningitis, or the inflammation of the protective layer around the brain and spinal cord
- Back pain
And during the initial stages of infection: a fever, vomiting, headache, fatigue, and stiff and painful legs, arms, and neck.
Remember, most people who get infected with this virus have no symptoms, and of those that experience symptoms rarely develop paralysis or death.
In order to diagnose polio, we not only look at the signs and symptoms we outlined, but also take samples of throat secretions, stool samples, and even the fluid that surrounds your brain and spinal cord, called cerebrospinal fluid, through a procedure known as a spinal tap in order to help identify the virus in those samples. The presence of the virus in any of those samples combined with the signs and symptoms I outlined would then help establish a diagnosis of this disease.
Treatment and Prevention
For the unfortunate few who get affected with this disease and are diagnosed with it, there is unfortunately no treatment at all. Supportive care in the form of a good diet, pain-relievers, and ventilators to assist in breathing can be used.
That's why the most important thing anyone can do to avert the terrible consequences of polio some people experience is to get vaccinated against this virus and disease. The person you can thank for this vaccine, the man who developed the vaccine for polio, was called Jonas Salk.
Jonas Salk, the man who developed the vaccine for polio, did so because polio is a contagious, virally induced disease that can cause paralysis and death.
The more technical term for polio is poliomyelitis and the virus responsible for causing polio is unsurprisingly known as the poliovirus. This virus is transmitted through the horizontal route, such as feces-contaminated water and respiratory secretions.
Polio typically affects children under five years of age, and in 1 of 200 infections will lead a person to develop irreversible paralysis. The reason this paralysis occurs is because the virus invades the spinal cord, damages the motor neurons there, and this damage doesn't allow the virus to properly signal the muscles of locomotion.
In order to diagnose polio, we not only look at the signs and symptoms we outlined, but take samples of throat secretions, stool samples, and even the fluid that surrounds your brain and spinal cord.
For the unfortunate few who get affected with this disease and are diagnosed with it, there is unfortunately no cure. That's why the most important thing anyone can do to avert the terrible consequences of polio some people experience is to get vaccinated against this virus and disease.
When this lesson is done, you should be able to:
- Describe the history of poliomyelitis
- Define the symptoms of the disease and how it spread
- Identify Jonas Salk
- Describe the treatment and prevention of polio