What causes polio?

Everyone may be very familiar with a disease, that is, polio. This disease was once popular in the 1970s. Now the incidence rate has been gradually controlled. This disease is more common in children. Patients will feel very uncomfortable during the onset. So, do you know what causes polio?

Within one day after invading the human body through the oropharyngeal or intestinal mucosa, the polio virus can reach local lymphatic tissues [3] such as tonsils, pharyngeal wall lymphatic tissues, intestinal wall collecting lymphatic 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 (first viremia) and reaches various non-neural tissues such as the respiratory tract, intestines, skin mucosa, heart, kidneys, liver, pancreas, adrenal glands, etc. on the third day to multiply, especially in the lymphatic tissues throughout the body, and enters the blood circulation again in large quantities on the fourth to seventh days (second viremia). If the specific antibodies in the blood circulation are sufficient to neutralize the virus at this time, the disease will stop at this point and form abortive poliomyelitis.

Only upper respiratory tract and intestinal symptoms occur without neurological lesions [4]. In a small number of patients, due to the strong virulence of the virus or insufficient antibodies in the blood to neutralize it, the virus can flow through the blood-brain barrier and invade the central nervous system. Severe lesions may cause paralysis. Occasionally, the virus can also spread along the peripheral nerves to the central nervous system. 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.

The most prominent pathological changes of poliomyelitis are in the central nervous system (this virus is neurotropic). 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, scattered inflammatory lesions can be seen on the pia mater, the arachnoid membrane is rarely affected, and 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 flows through the blood-brain barrier and invades the central nervous system, and spreads along the nerve fibers, causing non-paralytic symptoms; if the motor neurons are severely damaged, it will lead to muscle paralysis, causing paralytic symptoms.

Through the above, we can see what the causes of polio are. I wonder if you have a better idea about the prevention of this disease. But for now, vaccination is still an effective preventive measure. At the same time, we should also pay attention to a proper diet, exercise, and strengthen our physical fitness. In this way, it will become difficult for the disease to invade.