Poliomyelitis

　　Poliovirus (poliomyelitis virus) belongs to the enterovirus genus of the Picornaviridae family. Under an electron microscope, the virus appears as small spherical particles with a diameter of 24～30nm, in the form of round granules, containing single-stranded ribonucleic acid, with a nucleic acid content of 20％～30％. The viral capsid is composed of 32 capsomeres, with each particle containing four structural proteins, namely VP1～VP4. VP1 has a special affinity for human cell membrane receptors and is related to the pathogenicity and toxicity of the virus.

　　1. Resistance Poliovirus is insensitive to all known antibiotics and chemotherapeutic drugs, can withstand general concentrations of chemical disinfectants, such as 70% ethanol and 5% coal tar soap solution, 0.3% formaldehyde, 0.1mmol/L hydrochloric acid, and (0.3～0.5)×10-6 free chlorine can quickly inactivate it, but it can be protected in the presence of organic matter, and can be completely inactivated by heating to 56℃ for 30 minutes, but it can be preserved for several years in frozen conditions, can be preserved for several weeks in a refrigerator at 4℃, and can survive for several days at room temperature. It is sensitive to ultraviolet light, dryness, and heat, and can survive for months in water, feces, and milk. Magnesium chloride can enhance the virus's resistance to temperature, so it is widely used for preserving attenuated live vaccines.

　　2.抗原性质 利用血清中和试验可分为Ⅰ，Ⅱ，Ⅲ三个血清型，每一个血清型病毒都有两种型特异性抗原，一种为D(dense)抗原，存在于成熟病毒体中，含有D抗原的病毒具有充分的传染性及抗原性;另一种为C(coreless)抗原，存在于病毒前壳体内，含C抗原的病毒为缺乏RNA的空壳颗粒，无传染性，病毒在中和抗体的作用下，D抗原性可转变为C抗原性，失去再感染细胞的能力，加热灭活的病毒即失去VP4和核糖核酸，而成为含有C抗原的病毒颗粒，应用沉淀反应与补体结合试验可检出天然D抗原及加热后的C抗原。

　　3.宿主范围和毒力 人类是脊髓灰质炎病毒的天然宿主和储存宿主，猴及猩猩均为易感动物，病毒与细胞表面特异受体相结合并被摄入细胞内，在胞质内复制，同时释出抑制物抑制宿主细胞RNA和蛋白质的合成。

　　天然的脊髓灰质炎病毒称为野毒株，在实验室内经过减毒处理的病毒株称为疫苗株，疫苗株仅当直接注射到猴中枢神经系统时才能引起瘫痪，而对人神经细胞无毒性，疫苗株病毒，特别是Ⅲ型病毒，在人群中传播时可突变为具有毒性的中间株，对野毒株和疫苗株的最可靠鉴别方法是进行核酸序列分析。

　　原先存在于肠道内的其他肠道病毒(柯萨奇和埃可病毒等)，可对口服疫苗株病毒产生干扰现象，使之不能定居于肠黏膜上及进入血液循环，从而降低其刺激免疫系统产生抗体的能力。

　　脊髓灰质炎的并发症有哪些？以下就是关于脊髓灰质炎的并发症的具体介绍：

　　1水电解质紊乱：呼吸肌瘫痪患者长期使用人工呼吸机时易导致水和电解质紊乱高热出汗呕吐腹泻不能进食及血气改变皆可引起严重生化紊乱补液过多可引起水肿和低钠血症

　　2心肌炎：病毒可直接侵犯心肌引起心电图T波ST段和P-R间期改变见于10％～20％病例

　　3高血压：可由下列因素引起：①缺氧;②由于下视丘受累导致持续性高血压进而引起视网膜病惊厥和神志改变

　　4肺水肿与休克：发病机制未明常见于死亡病例的末期

　　5消化道穿孔与出血：曾观察到胃和十二指肠的急性扩张盲肠穿孔十二指肠胃和食管的急性溃疡整个胃肠道的多发性糜烂伴有大出血和肠麻痹等

　　6 Atrophy of the lung and pneumonia: Common in severe bulbar paralysis (involvement of the 9th and 10th cranial nerves) or bulbospinal paralysis, leading to paralysis of respiratory muscles or swallowing muscles, which may be exacerbated by tracheotomy. Common pathogens are Staphylococcus aureus or Gram-negative bacteria, which are often resistant to commonly used antibiotics. Chemical prophylaxis is also ineffective.

　　7 Urinary tract infection: Often associated with indwelling urinary catheters, chemotherapy and tidal drainage are usually ineffective. Due to prolonged bed rest and mobilization of calcium, renal calculi and concurrent infection may occur. Increasing fluid intake, limiting calcium-rich foods, acidifying urine, using salicylate preparations, and early activity can reduce the incidence of calculi.

　　8 Arthritis: In the recovery period of paralytic cases, a syndrome similar to rheumatoid arthritis may occur, characterized by redness, swelling, pain, and tenderness in large joints.

　　The incubation period ranges from 3 to 35 days, usually 7 to 14 days, and can be divided into four types in clinical practice: asymptomatic type, abortive type, paralytic type, and atypical type.

　　1. Asymptomatic type (i.e.,隐性感染), accounting for 90% to 95% of all infected individuals, shows no symptoms after infection, but the virus can be isolated from the throat and feces. A fourfold increase in specific neutralizing antibodies can be detected in paired serum samples taken 2 to 4 weeks apart.

　　2. Abortive type, accounting for 4% to 8% of all infected individuals, is characterized by symptoms such as fever, fatigue, headache, drowsiness, sore throat, nausea, vomiting, constipation, and without symptoms of central nervous system involvement. The clinical manifestations of this type are non-specific, and the following three syndromes have been observed: ① Upper respiratory tract inflammation, with varying degrees of fever, discomfort in the throat, which may have symptoms of a common cold, congestion and edema of the lymphoid tissue in the throat; ② Gastrointestinal dysfunction, with nausea, vomiting, diarrhea, or constipation, abdominal discomfort, which may be accompanied by moderate fever; ③ Influenza-like symptoms, with fever and symptoms similar to influenza, which last for about 1 to 3 days and then recover. In the early stage, poliovirus can be isolated from the throat, feces, and blood, and specific neutralizing antibodies and complement fixation antibodies can be detected in the serum during the convalescent period.

　　3. Paralytic type, characterized by prodromal symptoms, meningeal irritation signs, and cerebrospinal fluid changes. The prodromal symptoms are similar to those of the abortive type, with meningeal irritation signs appearing a few days later. Patients may experience headache, neck pain, back pain, vomiting, stiffness in the neck and back, positive Kernig and Brudzinski signs, tripod sign (patients extending their arms backward to support their body when sitting up in bed), and Hoyne sign (the shoulder can be elevated when lying on the back, causing the head to tilt backward). These signs may also be positive. Cerebrospinal fluid examination shows changes consistent with aseptic meningitis (mildly elevated white blood cell count and protein content, normal sugar and chloride levels, no growth on culture), with no changes in neurological and muscular function throughout the course of the disease. This type is difficult to distinguish from aseptic meningitis caused by other viruses in clinical practice and can only be diagnosed by virological or serological tests. Patients usually defervesce within 3 to 5 days, but meningeal irritation signs may persist for up to 2 weeks.

　　4. Paralytic Type

　　This type accounts for 1% to 2% of all infected individuals, and its characteristic is that in addition to the clinical manifestations of non-paralytic type, there is also involvement of the gray matter of the anterior horn of the spinal cord, brain, or cranial nerves. According to the site of the lesion, it can be divided into 4 types: spinal type, medullary type, brain type, and mixed type, with the spinal type being the most common. This type is divided into the following 5 stages (Table 1).

　　(1) Prodromal Phase: The symptoms of this phase are similar to those of abortive type, with upper respiratory tract inflammation being the main symptom in children, and general muscle, bone pain, and skin hypersensitivity in adults. After 1 to 2 days of fever, followed by a 4 to 7-day afebrile period, then fever again, entering the preparatory phase. Bifocal fever pattern is mainly seen in 10% to 30% of cases in children. This phase corresponds to the second viremic stage, with cerebrospinal fluid remaining normal. Most cases, including adult cases, lack the prodromal phase and enter the preparatory phase directly.

　　(2) Preparatory Phase: The characteristics of this phase are fever, headache, vomiting, and muscle pain and spasm. Fever runs throughout the stage, but the temperature is not very high. Headache affects the neck and back and can radiate to the two thighs. Due to muscle pain, movement is often limited and muscle spasms may occur, often causing a false impression of paralysis. Occasionally, there may be abnormal skin sensation, hypersensitivity, or involuntary muscle spasms. At this time, in addition to the above-mentioned tripod sign and Hoyne sign, the Laségue sign (pain when the knee is extended and the hip joint is flexed) is also often positive. About half of the patients have neck stiffness and a positive Kernig sign, and there are changes in cerebrospinal fluid, indicating that the virus has entered the central nervous system and caused meningitis. Patients may have transient loss of consciousness or drowsiness, abdominal pain, constipation, bloating, and urinary retention. This phase usually lasts for 3 to 4 days, occasionally as short as 36 hours or as long as 14 days, and in rare cases, this phase may be lacking and the patient may directly enter the paralysis phase.

　　(3) Paralysis Phase: Paralysis occurs suddenly during the peak of fever and myalgia, or it may start from mild paresis and gradually worsen. At the same time, meningeal irritation signs gradually regress. Paralysis is of lower motor neuron nature, manifested by disappearance of tendon reflexes, decreased muscle tone, disordered vascular and respiratory functions, muscle atrophy, and electromyogram evidence of anterior horn lesions of the spinal cord. Paralysis usually reaches its peak within 48 hours, with mild cases no longer progressing, while severe cases may continue to worsen for 5 to 10 days. Pain is asymmetrical and can affect any muscle group, presenting as monoparesis, diplegia, paraplegia, or quadriplegia. Unilateral lower limb paralysis is most common in children, followed by bilateral lower limb paralysis, while in adults, quadriplegia, paraplegia, dysfunction of bladder function, and paralysis of respiratory muscles are more common, and males are more severe than females. This phase lasts for 2 to 3 days and usually stops progressing when body temperature returns to normal.

　　① Spinal Cord Palsy: When the cervical enlargement of the spinal cord is damaged, paralysis of the neck muscles, shoulder muscles, upper limbs, and diaphragm can occur. When the thoracic segment of the spinal cord is affected, there can be paralysis of the neck muscles, intercostal muscles, upper abdominal muscles, and spinal muscles. In both cases, difficulty in breathing can occur. When the lumbar enlargement of the spinal cord is affected, paralysis of the lower limbs, lower abdominal muscles, and lower back muscles can occur. In the first two weeks after the onset of paralysis, local pain is common and gradually disappears as the recovery period progresses.

　　In the early stage of paralysis, the abdominal wall and cremasteric reflexes may disappear for a short time (or throughout the course of the disease). Usually, there is no pathological reflex of the pyramidal system. In the early stage, there is often hyperesthesia of the skin, but the sensation does not disappear. Severe cases may have autonomic dysfunction, such as tachycardia, hypertension, sweating, and cyanosis and coldness of the affected limbs. When the trunk muscle group becomes paralyzed, the head cannot be held up straight, sitting up or turning over is impossible. The paralysis of the diaphragm and intercostal muscles manifests as difficulty in breathing, shallow breathing, weak coughing, and interrupted speaking. Physical examination may reveal restricted expansion of the thoracic cage (intercostal muscle paralysis) and an inverted abdomen during inhalation rather than an outward convexity, an abnormal phenomenon visible during X-ray fluoroscopy when the diaphragm is paralyzed. Bladder muscle paralysis can lead to urinary retention or incontinence. Intestinal and abdominal muscle paralysis can result in stubborn constipation due to the inability of the patient to defecate automatically. Abdominal muscle paralysis may also be accompanied by local bulging of the abdominal wall and the disappearance of abdominal reflexes.

　　On the 5th to 6th day of paralysis, with the gradual decrease in body temperature, paralysis stops developing. However, in about 10% of cases, paralysis can continue for up to one week after the fever subsides.

　　② Medullary Palsy: Medullary palsy accounts for 5% to 35% of all cases of paralysis, with approximately 85% of the cases having a history of tonsillectomy within one month before the onset. The incidence of pure medullary type does not exceed 10% of all paralysis cases and is more common in children. In adults, medullary type is often accompanied by spinal cord symptoms. Due to the different locations of the lesions in the brainstem, various symptoms can occur.

　　Brainstem Palsy: Commonly, the damage to the Xth and VIIth cranial nerves is observed, but other cranial nerves such as the IXth, XIth, XIIth, IIIrd, IVth, and VIth pairs can also be involved. Brainstem palsy is mostly unilateral, and when the Xth pair of cranial nerves become paralyzed, there is a hoarse voice, regurgitation of liquid food through the nose, accumulation of saliva and food in the oropharynx, difficulty in breathing, and difficulty in speaking. When the VIIth pair of cranial nerves are affected, facial paralysis occurs. When the IXth pair of cranial nerves are paralyzed, there is difficulty in swallowing, coughing while eating. When the XIth pair of cranial nerves are paralyzed, in addition to difficulty in swallowing, there are symptoms such as weak neck, drooping shoulders, and the head tilting forward or backward. When the XIIth pair of cranial nerves are invaded, difficulty in swallowing can also occur, in addition to the tongue extending outward and tilting towards the affected side, as well as difficulties in mastication and speaking. When the IIIrd and VIth pairs of cranial nerves are affected, they can cause ocular muscle paralysis and ptosis of the eyelids.

　　Respiratory center damage: When the reticular tissue in the ventral lateral aspect of the medulla is damaged, it can lead to respiratory disorders, such as shallow and irregular breathing, double inspiration, prolonged intervals between breaths, and apnea. The most significant sign of hypoxia is a rapid and irregular pulse (the heart rate in children's cases can reach about 200 beats/min), irregular heartbeat, and a rise in blood pressure followed by a gradual decrease. Patients may be restless initially, and then become confused and enter a coma. Seizures may occur occasionally.

　　Vascular motor center damage: When the reticular tissue in the ventral lateral aspect of the medulla is damaged, it can lead to circulatory failure. Initially, patients may present with erythema, tachycardia or bradycardia, followed by a decrease in blood pressure, weak pulse, and arrhythmia. The limbs become cold, and the skin turns cyanotic. The heart stops beating before the breathing stops. Patients often experience symptoms such as restlessness, delirium, and coma due to hypoxia, and may even have convulsions.

　　③ Brain type: Patients can present solely with encephalitis, or it can coexist with bulbar type or spinal cord type. Diffuse encephalitis is characterized by disturbance of consciousness, high fever, delirium, tremors, convulsions, coma, rigid paralysis, etc. Focal encephalitis is characterized by localization symptoms of the brain, and in the recovery period, dyslexia, clonic seizures, or epilepsy-like grand mal seizures may occur.

　　④ Mixed paralysis: It has clinical manifestations of both spinal cord paralysis and bulbar paralysis, and can have various combinations, such as limb paralysis, brain nerve paralysis, respiratory center damage, and vascular motor center damage.

　　(4) Recovery period: After 1-2 weeks after the acute phase, the paralyzed limbs gradually recover, and muscle strength also gradually increases, usually starting from the distal part of the limbs, such as the toes of the lower limbs, followed by the tibia and thigh. The reflexes gradually return to normal with the recovery of voluntary movement. The affected limb recovers faster in the first 3-6 months, and although there is still improvement afterwards, the speed is slower. Mild cases can recover well within 1-3 months, while severe cases often require 6-18 months or even longer to recover.

　　(5) Post-infection period: Some affected muscle groups may not recover due to severe nerve damage, leading to persistent paralysis and muscle contracture, and can lead to limb or trunk deformities (due to imbalance of muscle groups), such as kyphosis or scoliosis, clubfoot varus or valgus, etc., skeletal development is also hindered, thus seriously affecting the growth and development of children.

　　The immune effect of poliomyelitis vaccine is good.

　　(1) The earliest adopter of inactivated poliomyelitis vaccine (Salk vaccine) for active immunity has a definite protective effect on susceptible individuals after intramuscular injection. Since it does not contain live vaccine, it is also very safe for immunodeficient individuals. Some countries have achieved significant effects in controlling and almost eradicating poliomyelitis by using inactivated vaccines alone. However, the short duration of immunity induced by inactivated vaccines requires repeated injections, and it does not cause local immunity. The high cost of preparation is also a shortcoming. But in recent years, improved preparations can induce 3 types of antibodies in 99% of vaccinated individuals after 3 doses at the 2nd, 4th, and 12-18th months, and maintain them for at least 5 years.

　　Attenuated live vaccines (Sabin vaccine, Oral polio-virus vaccine, OPV) are currently used more frequently. This live vaccine virus has been cultured and passed through multiple generations, and has little or no toxicity to the human nervous system. After oral administration, it can replicate in the intestinal tissues of susceptible individuals, causing a rapid increase in homotypic neutralizing antibodies in the body. At the same time, due to the production of secretory IgA, the immunity of the intestines and pharynx is also enhanced, which can eliminate invasive wild virus strains and cut off their spread in the population. The live vaccine virus can also be excreted from the body, infecting contacts and indirectly providing them with immunity, hence its better immunogenicity. Now, three types of sugar pill vaccines have been produced, which can be stored for 5 months at 2-10°C, 10 days at 20°C, and only 2 days at 30°C, so it is still necessary to pay attention to cold storage (4-8°C). Children aged 2 months to 7 years are the main target group for vaccination, but other age children and susceptible adults should also receive the vaccine. Large-scale vaccination should be carried out in winter and spring, and it is recommended to take 2 or 3 doses on an empty stomach, avoiding the use of hot water to take the vaccine to prevent inactivation of the virus in the vaccine and loss of its efficacy. The sugar pill vaccines are divided into Type 1 (red), Type 2 (yellow), Type 3 (green), mixed Type 2 and 3 sugar pill vaccine (blue), and mixed Type 1, 2, and 3 sugar pill vaccine (white). They should be taken starting from 2 months of age, in three doses, and can be taken in order, one tablet each of Type 1, 2, and 3, or one mixed tablet of Type 1, 2, and 3. The latter has been proven to have better immunogenicity, fewer doses, and is less likely to be missed. Therefore, China has gradually shifted to using the three-type mixed vaccine, and each dose should be taken at least 4-6 weeks apart, preferably every 2 months, to prevent possible interference. To enhance immunity, it can be repeated annually for 2-3 consecutive years, and another dose should be taken before the child starts school at 7 years old. Type-specific antibodies can be produced in the body about 2 weeks after oral vaccination, reaching a peak within 1-2 months and then gradually decreasing. By 3 years, half of the children's antibodies have significantly decreased.

　　Oral vaccines rarely cause adverse reactions, occasionally mild fever, diarrhea, patients with active tuberculosis, severe rickets, chronic heart, liver, and kidney diseases, as well as those with acute fever, should not take the vaccine temporarily. There are reports suggesting that after repeated passages through the human intestinal tract, the vaccine virus strain may increase its neurotoxicity in monkeys. In recent years, cases of paralysis have been confirmed to be caused by vaccine strain viruses in countries that commonly use OPV. Most of these cases occur in immunocompromised individuals, so it is currently believed that attenuated live vaccines should not be used in immunocompromised individuals, whether due to congenital immune deficiency or secondary immune deficiency caused by medication, infection, or tumor. It is also recommended to avoid contact with those who have taken OPV. Some advocates suggest that such patients should first receive inactivated vaccines and then be boosted with attenuated live vaccines, but the majority prefer to use inactivated vaccines only.

　　(2) Passive immunization: For young children who have not received vaccines, pregnant women, medical personnel, immunocompromised individuals, after tonsillectomy and other local surgeries, if they come into close contact with patients, they should be given intramuscular injections of gamma globulin as soon as possible. The dose for children is 0.2-0.5ml/kg, or 6-9ml of placental globulin, once a day, for two consecutive days. The immunity can be maintained for 3-6 weeks.

　　(3) Isolate patients. At least 40 days of isolation should be maintained from the onset of the disease, with emphasis on respiratory and intestinal isolation in the first week. Excreta should be disinfected with 20% bleaching powder, utensils soaked in 0.1% bleaching powder clear solution or boiled for disinfection, or exposed to the sun for two days. The ground should be disinfected with lime water. The hands of those in contact should be soaked in 0.1% bleaching powder clear solution, or disinfected with 0.1% peracetic acid. Close contacts should be isolated and observed for 20 days.

　　(4) Pay attention to daily hygiene, keep the environment clean, eliminate flies, cultivate good hygiene habits, etc., are very important. During the epidemic period, children should avoid crowded places, avoid overexertion and catching a cold, postpone various preventive injections and non-urgent surgeries, etc., to prevent acute infection from turning into paralysis.

　　What examinations are needed for poliomyelitis? The following is a specific introduction to the examinations for poliomyelitis:

　　(1) Cerebrospinal fluid

　　Abnormal appearance, slightly turbid, with slightly increased pressure and cell count (25-500/mm3) usually appears before paralysis. Early on, neutrophils are predominant, followed by monocytes. After fever subsides, they quickly return to normal. Glucose may slightly increase, chloride is mostly normal, protein slightly increases and persists for a longer time. In a few patients, the cerebrospinal fluid may remain normal throughout.

　　(2) Peripheral blood picture

　　White blood cells are usually normal, but can increase in the early stage and secondary infection, with neutrophils as the main type. The erythrocyte sedimentation rate increases in the acute phase.

　　(3) Virus isolation or antigen detection

　　The virus can be isolated from the nasopharynx and feces within one week of onset, and feces can remain positive for 2 to 3 weeks. The significance of virus isolation from blood or cerebrospinal fluid in the early stage is greater. Generally, tissue culture is used for isolation, while PCR methods for detecting enterovirus RNA are faster and more sensitive than tissue culture in recent years.

　　(4) Serological examination

　　The titer of specific immune antibodies reaches its peak by the end of the first week, especially the rise of specific IgM is faster than IgG. Neutralization tests, complement fixation tests, and enzyme-labeled methods can be used for detection. Among them, neutralization tests are more commonly used due to their longer positive duration. A fourfold or more increase in the titer of double serum samples can be diagnosed. The complement fixation test becomes negative quickly, indicating a negative result, while a positive neutralization test often suggests previous infection; both positive results suggest recent infection. Recently, immunofluorescence technology for detecting antigens and specific IgM monoclonal antibodies, and enzyme-labeled methods for examination, are helpful for early diagnosis.

　　Patients' diet should be given according to medical advice, starting with thin and soft food and gradually increasing other foods as the body adapts. It is important to avoid excessive oils and to reasonably match sugar, fat, protein, minerals, vitamins, and other foods.

　　Patients should choose high-protein, high-vitamin, and easily digestible foods, and through reasonable nutrition matching and appropriate cooking, try to improve the appetite of patients, so that the nutrition and energy in the diet of patients can meet the needs of the body.

　　Patients should not consume foods and strongly stimulating foods that are harmful to the condition, such as chili, especially for patients in the acute stage and those with yin deficiency and fire excess type should be best avoided.

　　The treatment of this disease by modern Chinese medicine was first reported in 1954. In the mid-1950s, clinical data increased rapidly, and various methods such as traditional Chinese medicine, acupuncture, or the combination of acupuncture and medicine were used in treatment. From the late 1960s to the mid-1970s, traditional Chinese medicine mainly treated the disease by excavating traditional prescriptions, and acupuncture created the method of acupoint stimulation and ligation, which had a good effect on improving the muscle strength of paralyzed limbs and correcting some degree of deformity. In the past ten years or so, in addition to the above methods, helium-neon laser acupoint irradiation, electric needle, and needle penetration were also added, which improved the therapeutic effect. It is reported that the treatment effect of the initial stage (acute stage) is relatively good, with an internal administration cure rate of more than 80% and a total effective rate of 100%. If the disease is not treated in the early stage or treated improperly, leading to limb paralysis or paralysis, the treatment effect is poor, and the longer the disease lasts, the worse the effect. The basic cure rate of acupuncture treatment for children's paralysis sequelae is 30% to 40%, with an effective rate of more than 90%. Therefore, early detection and early treatment are the key to preventing paralysis or muscle atrophy disability.