How Does Polio Affect The Nervous System?

Poliomyelitis caused by poliovirus is a crippling disease that mostly affects children below the age of three years and adults with autoimmune disorders and special conditions. Although the symptoms are varied, the virus mainly attacks the nervous system to the point where it completely destroys the cells of the spinal cord resulting in paralysis.

How does poliovirus enter the body

Poliomyelitis can result from the infection by any one of the three related poliovirus types, commonly known as types P1, P2, and P3. These viruses are the members of the enterovirus or picornavirus family that are transmitted from one person to another. The mode of transmission can be by oral contact with secretions or faecal material from an infected person passed into the food and water of a healthy person. Once inside the body, the virus can reproduce in the nasal tract and in some specialized cells in the intestines and ultimately enter the bloodstream.

Destroying the nervous system

Through the blood and lymphatic vessels, the virus can reach all parts of the body. It can then invade the central nervous system, and spreads along all the nerve fibres. On multiplication within the nervous system, the virus slowly starts destroying the motor neurons or nerve cells responsible for taking commands from the brain to the different parts of the body. These nerves are connected to the skeletal muscles that allow voluntary movement by any individual. This impedes any voluntary movement and results in paralysis. Once affected nerve cells cannot regenerate, and so the affected muscles lose all their functions from lack of any nervous signals to activate them. This condition is termed acute flaccid paralysis or AFP.

In patients with poliomyelitis, most commonly the muscles of the legs get affected the worst followed by those of the arm muscles. In cases of severe paralysis, the muscles of the trunk, thorax, and abdomen, are also affected. Sometimes the poliovirus also affects the motor neurons supplying to the brain stem. This reduces the breathing capacity of the patient and causes difficulty in talking and eating, making respiratory support compulsory.

Once a person is infected, there is no cure available. The person has to rely on supportive treatment only with low to moderate recovery rates. The World Polio Day observed on the 24th of October raises awareness about poliovirus, the debilitating effects of the disease, and the polio vaccine. With widespread vaccination and awareness, reported cases of polio have dropped by 99 per cent. The World Health Organization has declared South East Asia completely free of polio and projects complete eradication of the virus in the foreseeable future.