The Disease and the Symptoms![]() Polio, (poliomyelitis) is a communicable disease of humans caused by a human enterovirus of the Picornaviridae family. The virus is composed of a single-stranded, positive-sense RNA genome and a protein capsid. If the virus leaves the intestinal tract, it enters the bloodstream and attacks the nervous system and causes nerve damage. This can cause serious problems such as paralysis, breathing problems and even death. In about 95% of cases, Polio actually produces no symptoms at all. This is called asymptomatic polio. In the 4% to 8% of cases in which there are symptoms is called symptomatic polio, and here, the disease comes in three forms:
2. Non-Paralytic Polio- A more serious form associated with aseptic meningitis. Can show neurological symptoms such as:
3. Paralytic Polio- The virus leaves the intestinal tract and enters the bloodstream, attacking the nerves. The virus may affect the nerves governing the muscles in the limbs and the muscles necessary for breathing, causing respiratory difficulty and paralysis of the arms and legs. The symptoms include most of the neurological symptoms faced during non-paralytic polio such as muscle spasms and limb pain, but also include some muscles losing tone and becoming flaccid. There are categories of Paralytic Polio based on which muscles/nerves are getting affected:
Which body systems and organs are affected?![]() The virus attacks the central nervous system. Poliovirus enters through the mouth and multiplies in the throat and gastrointestinal tract, then moves into the bloodstream and is carried to the central nervous system where it replicates and destroys the motor neuron cells. Motor neurons control the muscles for swallowing, circulation, respiration, the trunk, arms, and legs. Human nerve cells have a protruding protein structure on their surface whose precise function is unknown. When poliovirus encounters the nerve cells, the protruding receptors attach to the virus particle, and infection begins. Once inside the cell, the virus interrupts the cell’s assembly process, and replicates thousands of copies of itself within hours. The virus kills the cell and then spreads to infect other cells, and in response to this, the immune system reacts. The infection of cells can result in paralysis, or even death, when respiratory muscles such as the diaphragm controlling breathing, gets infected. In Spinal paralytic polio, the virus may affect muscles on both sides of the body, however, more often, the paralysis is asymmetrical. Any limb or a combination of limbs may be affected; eg. one leg, one arm, or both legs and both arms. In Bulbar paralytic polio, when the virus attacks the brainstem, it can result in facial distortions, problems swallowing and breathing.
Visit: http://amhistory.si.edu/polio/activities/lifecycle/index2.htm to watch how poliovirus attacks the nerve cells |
Poliomyelitis | What is the disease? |