Hepatitis A

　　甲型肝炎病毒HAV是小核糖核酸病毒科的一员，为嗜肝RNA病毒属。HAV经口进入体内后，经肠道进入血流，引起病毒血症，约过一周后到达肝脏，随后通过胆汁排入肠道并出现粪便中。粪便排毒能维持1-2周。病毒侵犯的主要器官是肝脏，咽部和扁桃体可能是HAV肝外繁殖的部位。HAV引起肝细胞损伤的机制尚未明确，一般认为HAV不直接引起肝细胞病变，肝脏损害是HAV感染肝细胞的免疫病理反应所引起的。

　　1、传染源
　　甲型肝炎患者和无症状感染者为传染源，甲型肝炎患者仅从粪便中排出病原体，血液中HAV主要出现在黄疸发生前14-21天，在此期患者的血液有传染性，有报道通过输血传播，但黄疸发生后患者血液通常无传染性。患者在起病前2周和起病后1周从粪便中排出HAV的数量最多，此时传染性最强。但至起病后30天仍有少部分患者从粪便中排出HAV。

　　2、传播途径
　　甲型肝炎以粪口途径为主要传播途径，粪口传播的方式是多样的，一般情况下，日常生活接触传播是散发性发病的主要传播方式，因此在集体单位如托幼机构，学校和部队中甲型肝炎发病率高。水和食物的传播，特别是水生贝类如毛蚶等是甲型肝炎爆发流行的主要传播方式。

　　3、易感性与免疫力
　　人群未注射甲肝疫苗者对HAV普遍易感，患过甲型肝炎或感染过甲型肝炎病毒的人可以获得持久的免疫力。

　　甲肝以急性肝炎为主，无慢性化，预后好，同时感染或重叠感染其他嗜肝病毒时，病情可加重甚至可以发生重型肝炎。重型肝炎约占全部甲肝病例的0.2％－0.4％，病死率高。急性肝炎的并发症较少，其中比较常见的胆囊炎，偶见心包炎、结节性多动脉炎。

　　The incubation period of hepatitis A is an average of 30 days (5-45 days), mainly manifested as acute hepatitis, divided into acute jaundice type and acute non-jaundice type. The typical acute jaundice type of hepatitis A is characterized by an acute onset, with early symptoms such as chills, fever, general weakness, loss of appetite, aversion to greasy food, nausea, vomiting, abdominal pain, liver area pain, diarrhea, and the urine color gradually deepens to a dark tea color. A few cases may present with fever, headache, and upper respiratory symptoms as the main manifestations, which are easily misdiagnosed as upper respiratory tract infection. Before the jaundice appears, the early gastrointestinal symptoms are obvious and are easily misdiagnosed as gastritis or indigestion.

　　With the progression of the disease, the above自觉symptoms decrease, fever subsides, but the urine color continues to deepen, the sclera of the eyes and the skin appear jaundice, reaching a peak in about 2 weeks, accompanied by lightening of stool color, skin itching, liver enlargement, fullness, tenderness, and percussion pain. Some patients may have splenomegaly. These symptoms can last for 2-6 weeks. During the recovery period, jaundice gradually subsides, symptoms decrease to disappear, the liver and spleen shrink, and liver function gradually returns to normal. The total course of the disease is about 2-4 months.

　　The following are the preventive measures for hepatitis A:
　　1. Improve personal hygiene levels, widely carry out health education on diseases from the mouth. Wash hands with running water and wash tableware, bring your own tableware when eating at the unit, and develop the good habit of washing hands before and after meals.
　　2. The catering industry should seriously implement the Food Hygiene Law. Especially, the disinfection of tableware should be done well. Cafeterias and restaurants should implement a separate meal system or communal chopstick system. Primary and middle schools should provide hot water, and students should bring their own cups. Illegal catering stalls that do not meet health conditions or are unlicensed should be abolished.
　　3. Strengthen the protection of water sources, strictly prevent drinking water from being contaminated by feces. Strengthen the health supervision of raw aquatic products. Strengthen the health protection of the production area waters, prevent the pollution of feces and domestic wastewater. It is as far as possible to avoid eating potentially contaminated water, fresh fruits, vegetables, and shellfish foods, and do a good job in environmental hygiene and the harmless treatment of feces.
　　4. Kindergartens and nurseries should establish practical and feasible health systems and strictly implement the disinfection system for tableware and toilets. Children should implement the system of one towel, one cup per person. For full-time units, attention should also be paid to the disinfection of diapers. Toys used by each team should be strictly separated and corresponding disinfection treatments should be carried out.
　　5. Disinfection should also be carried out for the food, toilet, clothing, bedding, needles, and excreta of hepatitis A patients. The disinfection method should be adopted according to different disinfection objects, such as boiling, formaldehyde, strong glutaraldehyde, effective chlorine, and ultraviolet light to inactivate the virus.
　　6. Protect susceptible populations.

　　This disease can be diagnosed by the following examinations:

　　1. Laboratory examination

　　Blood and urine routine:The peripheral blood routine white blood cell count is generally reduced or within the normal range, accompanied by mild lymphocyte or mononuclear cell ratio increase. In the early stage of the disease, the urinary urobilinogen increases, and during the jaundice period, both bilirubin and urobilinogen in urine increase. Liver function tests, such as serum ALT, AST, and total bilirubin levels, are most useful. Studies have shown that the average peak ALT in patients with hepatitis A can reach 1952 IU/L, and AST can reach 1442 IU/L. Most apparent infectious cases are accompanied by an increase in serum total bilirubin levels.

　　2. Hepatitis A virological indicators
　　Anti-HAVIgM:It can be detected in serum about 1 week after onset. Its appearance is consistent with the time of clinical symptoms and abnormal laboratory indicators, reaching a peak in the second week. Generally, it lasts for 8 weeks, and a few patients may last for more than 6 months. However, some patients may be negative in the early stage of the disease and positive after 2-3 weeks. Therefore, for clinical suspected acute hepatitis A with negative anti-HAV IgM, 1-2 repeat tests should be performed to avoid missed diagnosis. Currently, anti-HAV IgM is a highly specific indicator for the early diagnosis of acute hepatitis A, and it has the advantages of simplicity and rapidity. Anti-IAVIgG is an indicator of past infection, as it is a protective antibody that can protect the body from re-infection and can be used for epidemiological surveys to understand susceptible populations.

　　Anti-HAV-IgA antibody:Also known as secretory antibody, mainly present in tears, saliva, urine, gastric juice, breast milk, and nasal secretions. IgA in gastric juice can be excreted into feces, and anti-HAV-IgA can be detected in the fecal extract of patients with hepatitis A. It can be used as an auxiliary diagnosis of hepatitis A. In addition, the detection of HAV in feces and serum hepatitis A ribonucleic acid (HAVRNA) also has diagnostic value, but it requires certain equipment and technology and is not routine as a routine examination item. In summary, for suspected acute hepatitis A patients with typical symptoms and significantly elevated transaminases, further examination of anti-HAV IgM can be used to confirm the diagnosis of hepatitis A.

　　Dietary precautions for the prevention of hepatitis A:
　　1. Disinfect tap water and well water:Strengthen the disinfection of drinking water, whether it is tap water, well water, river water, or pond water, it must be disinfected. Adding one crystal tablet of bleaching powder to 50 kilograms of water can kill hepatitis A virus; if there is an outbreak of hepatitis A, the amount of bleaching powder crystal can be appropriately increased.
　　2. Do not eat unclean food:Wash fruits and vegetables thoroughly before eating. Shellfish such as clam and scallop may adhere to hepatitis A virus, so do not eat them raw or semi-raw. Do not wash foods that are to be eaten directly, such as pickled vegetables and cold dishes, in potentially contaminated water.
　　3. Pay attention to the hygiene of tableware and tea sets:Do not hold banquets when there is an outbreak of hepatitis. Because hepatitis A patients may excrete the virus in their feces before the onset of symptoms, and holding a banquet during an outbreak of hepatitis A may expose guests to the risk of hepatitis A outbreak.
　　4. Early detection, early isolation, and early treatment:Before the symptoms of hepatitis A patients become obvious, they are highly infectious. Therefore, the earlier the discovery and isolation, the less the risk of transmission.

　　Most acute hepatitis A does not require special treatment. With proper rest, reasonable nutrition, and drug辅助treatment, the course of the disease can usually be self-limiting. The main measures are as follows:

　　1. Treatment
　　1. Rest For patients with non-jaundice hepatitis without obvious clinical symptoms, there is no emphasis on bed rest. During the acute stage of jaundice hepatitis, bed rest should be maintained until jaundice basically subsides, and for severe hepatitis, absolute bed rest should be maintained. During the recovery period, appropriate activity can be performed to facilitate recovery.

　　2. Appropriate Diet During the acute stage, patients should eat light, low-fat, vitamin-rich, and easily digestible food. During the recovery period, sufficient calories and high-protein diet should be provided. When severe hepatitis is complicated with hepatic encephalopathy, protein intake should be restricted to reduce the production of ammonia in the intestines and prevent hepatic encephalopathy.

　　3. Drug-assisted treatment
　　(1) Increase vitamins C, E, K, and drugs that promote energy metabolism such as adenosine triphosphate (ATP) and coenzyme A, and at the same time, blue root, hepatitis spirit, Qiangren, and traditional Chinese medicine formulas such as Yinchen Hao Decoction can be used together with清热利湿.
　　(2) For those with deep jaundice, Yinzhi Huang injection can be used for intravenous drip. For those with severe gastrointestinal symptoms or nausea and vomiting, appropriate fluid supplementation should be given;
　　(3) Severe hepatitis should take comprehensive measures, including
　　① Strengthen supportive therapy: Appropriately supplement fresh blood, fresh plasma, thrombin complex, etc.;
　　② Promote liver cell repair and regeneration: Growth factors for liver cells, glucagon-insulin (G-I) therapy can be used;
　　③ Treatment of hepatic encephalopathy: Reduce ammonia production and absorption from the intestines, which can be taken orally by lactulose. Adjust the ratio of branched-chain amino acids (hexapeptide) and other substances;
　　④ Treatment of cerebral edema: Use 20% mannitol in a timely and adequate manner, 1-2g/kg each time, and 80ml of 50% glucose injection, intravenous push, once/6h, alternate use;
　　⑤ Prevent and control secondary infection: If there is an infection, it is necessary to promptly select powerful antibiotics with no liver and kidney toxicity, and be vigilant about secondary infection;
　　⑥ Correct water and electrolyte imbalance;
　　⑦ Prevent renal insufficiency: Pay attention to supplementation when blood volume is insufficient.

　　4. Severe Hepatitis Comprehensive treatment measures should be taken, strengthening supportive therapy, blocking necrosis of liver cells, promoting regeneration of liver cells, and actively preventing and treating various complications.

　　II. Prognosis
　　The prognosis of hepatitis A is good, most patients have disappeared clinical symptoms within 3 months, liver function returns to normal, the longest not exceeding 6 months, and individual courses can last for more than 6 months. The possibility of becoming chronic is small, and there have been no chronic virus carriers found, and the mortality rate of severe cases is high.