What are the causes of polio?

Polio is a relatively serious infectious disease. Because of the appearance of polio symptoms, patients are very worried. We should face polio disease in life and actively go to the hospital for corresponding treatment. Polio can be cured. So what are the causes of polio? Let’s introduce it in detail below, I hope it will be helpful to everyone.

After the polio virus invades the human body through the oral, pharyngeal or intestinal mucosa, it can reach local lymphatic tissues within one day, such as tonsils, pharyngeal wall lymphatic tissues, intestinal wall lymphoid tissues, etc., grow and multiply, and excrete the virus locally. If the human body produces a large amount of specific antibodies at this time, the virus can be controlled locally, forming a latent infection; otherwise, the virus further invades the bloodstream (the first viremia), and reaches various non-neural tissues on the third day, such as the respiratory tract, intestines, skin mucosa, heart, kidneys, liver, pancreas, adrenal glands, etc., and multiplies, especially in systemic lymphatic tissues, and enters the blood circulation again in large quantities from the fourth to the seventh day (the second viremia). If the specific antibodies in the blood circulation are sufficient to neutralize the virus at this time, the disease will stop here, forming abortive poliomyelitis, with only upper respiratory tract and intestinal symptoms, but no nervous system lesions. A small number of patients may have strong virulence of the virus or insufficient antibodies in the blood to neutralize it, and the virus can flow through the blood-brain barrier with the blood and invade the central nervous system, and paralysis may occur in severe lesions. Occasionally, the virus can spread to the central nervous system along the peripheral nerves. Specific neutralizing antibodies are not easy to reach the central nervous system and intestines, so the virus remains in the cerebrospinal fluid and feces for a long time. Therefore, whether there are specific antibodies in the human blood circulation, the time of their appearance and the amount are important factors that determine whether the virus can invade the central nervous system.

Many factors can affect the outcome of the disease, such as cold, fatigue, local irritation, injury, surgery (such as preventive injections, tonsillectomy, tooth extraction, etc.), and low immunity, all of which may cause paralysis. Pregnant women are more likely to suffer from paralysis if they get sick. Older children and adult patients are more likely to suffer from paralysis. Boys are more likely to suffer from severe illness than girls, and paralysis is more common.

The most prominent pathological changes of poliomyelitis are in the central nervous system (the virus is neurotoxic). The lesions are scattered and asymmetric, and may involve the brain, midbrain, medulla oblongata, cerebellum and spinal cord. The main damage is to the spinal cord, followed by the brainstem, and the lesions of motor neurons are the most significant. The spinal cord is mostly damaged in the gray and white matter cells of the anterior horns of the cervical and lumbar segments, so quadriplegia is common clinically. Most brainstem centers and cranial nerve motor nuclei may be damaged, with lesions of the reticular structure, vestibular nuclei and cerebellar tegmental nuclei being the most common. Lesions rarely occur in the cerebral cortex, and even if there are lesions in the motor area, they are mostly mild. Sympathetic ganglia and peripheral ganglia lesions are occasionally seen, and scattered inflammatory lesions can be seen on the pia mater, with the arachnoid membrane rarely involved. Inflammatory changes occur in the cerebrospinal fluid. Most non-paralytic nervous system lesions are mild. After the polio virus enters the human body through the mouth, it invades the lymphatic tissue of the pharynx and intestines, forming a latent infection; if the antibody is low, the virus enters the blood circulation and causes viremia. If the body lacks immunity, the virus will flow through the blood-brain barrier and invade the central nervous system, and spread along the nerve fibers, causing non-paralytic symptoms; if the motor neurons are severely damaged, it will lead to muscle paralysis and cause paralytic symptoms.

Through our introduction of the causes of polio, I believe everyone has a better understanding of this issue. As long as everyone pays attention to maintaining good hygiene habits, this disease can be avoided. It is also recommended that parents pay attention to their children's physical changes. If something is wrong, they should be sent to the hospital for diagnosis and treatment immediately. Early treatment means early recovery. Finally, I wish all children can grow up healthily.