Gastrointestinal infection in SARS

　　1. Causes of Disease

　　SARS-CoV belongs to the family Coronaviridae and genus Coronavirus, which is an enveloped virus with a diameter of mostly 60-120 nm. The envelope has radiating petals or cilium-like protrusions. It is about 20 nm or longer, with a narrow base, resembling a crown, and similar to classical coronaviruses. The morphogenesis process of the virus is long and complex, with mature viruses being spherical or elliptical. There are significant differences in size and shape between mature and immature virus particles, which can appear in many strange shapes, such as kidney-shaped, mace-shaped, horseshoe-shaped, bell-shaped, etc., and are easily confused with cell organelles. In terms of size, the virus particles decrease from 400 nm at the beginning to 60-120 nm in the late mature stage. Diverse shapes of virus particles can also be seen in the specimens of patient autopsies.

　　According to the research of the WHO multicenter SARS collaboration group, SARS-CoV can survive at least 1-2 days at room temperature in urine and feces, more than 4 days in the feces of diarrhea patients (whose pH is higher than that of normal feces), and up to 24 hours on plastic surfaces. After placing the virus in cell culture supernatant at 4℃ and up to 80℃ for 21 days, the virus titer only slightly decreased. The virus titer in the cell culture supernatant decreased by one order of magnitude after being placed at room temperature for 2 days, and the virus titer decreased by about 10,000 units per 15 minutes after being heated to 56℃. Daily used disinfectants such as 750ml/L alcohol can make the virus lose its infectivity in 5 minutes, and chlorine-containing disinfectants can inactivate the virus in 5 minutes.

　　2, Pathogenesis

　　It has been observed that intestinal epithelial cells can be infected by SARS-CoV. Some believe that the main cause of diarrhea in SARS patients is early viralemia mainly caused by fever, followed by pulmonary inflammatory exudation and consolidation, which causes hypoxemia due to impaired ventilation, leading to non-specific damage to the gastrointestinal tract. Given the current immune pathogenesis theory, it cannot be excluded that the virus may cause damage to the gastrointestinal tract through direct or indirect immune mechanisms. The exact pathogenesis requires further study.

　　The structures of the stomach, intestines, and layers of the stomach wall were intact. The submucosal lymphatic tissue of the stomach, small intestine, and colon segments was reduced, with sparse lymphocytes and interstitial edema. In some cases, superficial erosion or ulcers were visible in the stomach.

　　Under endoscopic examination, there were no abnormalities found in the colonic mucosa and the distal ileum. The autopsy specimens also showed normal tissue structure under the microscope, with no evidence of villous atrophy, inflammation, bacterial infection, viral inclusions, or granulomas. In addition, apart from some autolysis changes, there were no abnormalities observed macroscopically or under light microscopy. The virus particles (60-90nm) observed in the colonic mucosa and distal ileum under electron microscopy matched with SARS-CoV, and the virus was confined to the epithelial cells. The intracellular virus particles may be contained within expanded rough endoplasmic reticulum. Virus particles were visible on the surface of microvilli, which may suggest that the virus leaves the surface of intestinal cells. There is still no evidence to show villous atrophy.

　　The systemic and respiratory symptoms of SARS patients with diarrhea are not special, possibly due to the timely admission of patients, and complications caused by diarrhea are not common.

　　Dehydration and acidosis are the main lethal causes of acute diarrhea. The carbon dioxide produced by metabolic processes in the body is exhaled through respiration, while the remaining waste products need to be transported by water through the kidneys and excreted from the body as urine. During dehydration, urine output decreases due to the loss of body water, and in severe cases, there may be no urine at all. This can lead to a reduction in the excretion of waste products produced by metabolism, causing them to accumulate in the body, leading to toxic symptoms in the body. The clinical manifestations, in addition to changes in respiration, can also include fatigue, weakness, and symptoms of the nervous system.

　　After a relapse of gastroenteritis with diarrhea, the digestive function of the human body gradually decreases, and the resistance of the intestines to diseases also weakens, which increases the burden on the gastrointestinal function, often leading to a recurrence of gastric disease.

　　Among 40 critically ill SARS patients reported, 8 had diarrhea, all of whom were elderly patients with fever upon admission, with initial fever over 39°C. These 8 patients all showed varying degrees of nausea, vomiting, decreased appetite, and diarrhea on the 2nd to 3rd day of the onset, with diarrhea less than 10 times per day, lasting for 3 to 8 days, and the stool was mostly yellow and watery, without abdominal pain.

　　In a study of 305 SARS cases treated in the Beijing area, 42 patients with gastrointestinal symptoms and acute gastrointestinal bleeding were the subjects. The statistics showed that 17 of the 42 SARS patients had abdominal pain, 29 had diarrhea, 7 had both abdominal pain and diarrhea, and 4 had gastrointestinal bleeding. The symptoms of all patients with abdominal pain or diarrhea were mild, and the duration was generally 1 to 2 days.

　　In a retrospective analysis in 2004, Cheng and others from Queen Mary Hospital, Hong Kong reported that 48.6% of SARS patients (69/142) developed diarrhea within (7.6±2.6) days after the onset of initial symptoms, reaching a peak in (8.8±2.4) days, with diarrhea frequency of 3 to 24 times per day, on average 5 times per day. However, after statistical analysis, it was considered that diarrhea was not related to the mortality rate.

　　Leung and others from the Prince of Wales Hospital, The Chinese University of Hong Kong, statistically analyzed 138 SARS patients admitted to the hospital, and watery diarrhea was the most common intestinal symptom. In 28 patients, watery diarrhea mostly appeared in the first week, with 53 patients showing diarrhea symptoms during the 3-week course, 8 patients had fever accompanied by diarrhea without respiratory symptoms, the stool generally did not contain blood or mucus, most abdominal pain was mild, and diarrhea was more frequent in the first week of the course, with an average duration of (3.7±2.7) days, most of the symptoms were self-limiting.

　　It is generally believed that the population is susceptible to SARS, with a lower infection rate among children. On April 15, 2003, relevant agencies in Hong Kong reported an outbreak of 321 SARS cases in the Tao Da Garden residential area, with 66% showing diarrhea symptoms; it is reported that the incidence of diarrhea in SARS patients varies significantly in different regions and countries, ranging from 24.5% to 73.9% in Beijing, 7.8% to 24.2% in Guangzhou, 38.4% to 53% in Hong Kong, 50% in Taiwan, and 24% in the Toronto area of Canada. This difference may be due to different diagnostic criteria in various places, and it is not yet clear whether it is related to the variation of the virus. The existing statistics cannot explain the statistical differences in the incidence of SARS combined with diarrhea in different age groups. Chinese data show that the elderly death group seems to have a higher incidence of diarrhea.

　　1, Stool routine

　　Mostly yellow watery, with a few white blood cells (1-6/HP) visible under the microscope. In cases with gastrointestinal bleeding, more red blood cells can be seen. Some patients have a slight increase in alanine aminotransferase (ALT). RT-PCR can detect the virus in the stool.

　　2, Blood routine

　　During the early to middle stage of the disease, the white blood cell count is usually normal or decreased, and the lymphocytes are commonly reduced. In some cases, the platelet count is also reduced, and the CD3+, CD4+, and CD8+ T cell subsets in the T cell subsets are significantly reduced. In the later stage of the disease, most can return to normal.

　　Most patients with SARS have chest X-ray abnormalities in the early stage of onset, mostly presenting as patchy or reticular changes. In the early stage of onset, it often presents as a single focus lesion, and the lesions increase rapidly in a short period of time, often involving both lungs or multiple lobes of a single lung. Some patients progress rapidly, presenting as large areas of shadow, and it is more common to involve the peripheral areas of both lungs. The manifestations such as pleural effusion,空洞 formation, and enlargement of hilar lymph nodes are less common. For patients who have no chest X-ray lesions but are clinically suspected of having the disease, chest X-ray examination should be re-examined within 1-2 days, and chest CT examination shows the most glass-like changes. The absorption and dispersion of lung shadows are slow; the changes in shadows may not be consistent with clinical symptoms and signs.

　　Therapeutic Food Recipes

　　1, Chinese Yam and Pork Ribs Soup:You need 75 grams of Chinese yam, 75 grams of lily, 50 grams of mulberry bark, and 500 grams of pork ribs or lean meat. Cooking method: wash the materials clean and put them all into a pot, add water and boil for one and a half hours before drinking the soup;

　　2, Radish and Mung Bean Soup:You need appropriate amounts of Chinese cabbage, white radish, and mung beans. Cooking method: wash the materials clean and cook them together into a soup, do not add salt, and eat the soup and vegetables together.

　　What should patients eat

　　Vitamin A, Vitamin B, Vitamin C, Vitamin E, folic acid, calcium, iron, zinc, selenium, and others all have immune functions. It is best to choose foods that contain a variety of nutrients as much as possible. There are many foods with a variety of nutrients, soybeans being the most cost-effective and delicious choice. Soybeans contain a large amount of protein, amino acids, carbohydrates, Vitamin A, Vitamin D, Vitamin B, Vitamin C, as well as calcium, phosphorus, zinc, selenium, and trace elements. Especially, soybeans are rich in various unsaturated fatty acids, isoflavones, soy lecithin, saponins, plant hormones, oligosaccharides, and many other bioactive factors. The vitamins present in the soy milk after deep processing can participate in the metabolic process of the body after consumption, promote growth and the formation of antibodies, enhance resistance to diseases, and have detoxifying effects.

　　Three, dietary strategies

　　1. Consume high-quality proteins.

　　High-quality animal proteins include lean meat, chicken, fish (especially deep-sea fish containing omega-3 fatty acids such as tuna, mackerel, etc.), seafood, low-fat dairy products, and eggs; plant-based proteins include legumes, tofu, and soy products, nuts, etc.

　　2. Eat 1 bowl of mixed rice every day.

　　Eat at least 1 bowl of mixed rice, or mixed grain bread, whole wheat products every day.

　　3. Eat a variety of colored vegetables and fruits.

　　You should eat three types of vegetables and two types of fruits a day; the more varieties, the better. A simple method is to distinguish by color.

　　Choose one green, one red, and one black vegetable. Eat at least 1 to 2 bowls of dark green leafy vegetables every day.

　　Eat one red, orange, or yellow vegetable per day, such as carrots, bell peppers, pumpkins, sweet potatoes, and chayote.

　　In addition, consume a moderate amount of black mushrooms and other mushrooms.

　　You should eat two types of fruits a day, choosing those rich in vitamin C. Fruits rich in vitamin C include watermelons, papayas, strawberries, citrus fruits, etc., and can be eaten alternately every day.

　　4. Eat garlic.

　　Whether eaten raw or cooked, eating 2 to 3 cloves of garlic, or half an onion, several sections of scallion, can achieve the effects of sterilization, infection prevention, and anti-cancer.

　　5. Drink yogurt.

　　Drinking 1 to 2 bottles of yogurt (200 to 300 milliliters) per day can help maintain a good immune system.

　　6. Take a multivitamin every day.

　　People with long working hours and high pressure are prone to imbalanced diets, and it is necessary to supplement vitamins.

　　Nutrition experts do not recommend taking single vitamin supplements; it is better to take a multivitamin.

　　7. Do not consume excessive fat.

　　Adult men can consume 55 to 66 grams of fat per day, while women can consume 45 to 55 grams, and it is not advisable to exceed this amount.

　　8. Eat less sugar.

　　It is suggested to start by drinking less sugary beverages and switch to unsweetened green tea, herbal tea, and fruit tea, of course, drinking plain water is also good. In addition, eating sweets should also be limited. (According to Shen Xiaofu's article in the 'Family Weekend Newspaper' on May 22) During the period of taking antibiotics, you can drink a cup of yogurt every day. The bifidobacteria in yogurt can not only alleviate the side effects of antibiotics but also promote digestion. Patients taking antibiotics can eat more foods rich in vitamin B group, such as soybeans, lean meat, green leafy vegetables, etc., to alleviate the adverse reactions caused by taking the medicine.

　　After taking antibiotics, you should not eat fruits, especially those with a sour taste, as they can greatly reduce the efficacy of the medicine, resulting in delayed treatment and serious consequences. Oral antibiotics are generally absorbed through the gastrointestinal tract. Most fruits (such as apples, apricots, cherries, grapes, oranges, tangerines, kiwis, etc.) contain a large amount of citric acid, malic acid, tartaric acid, and other acidic components. These fruit acids have a strong solubility and can destroy the stability of antibiotics in the gastrointestinal tract, promoting their dissolution and decomposition, thereby reducing the efficacy of the medicine significantly. The more sour the fruit, the greater the impact on the efficacy of the antibiotic. Therefore, it is recommended not to eat any fruits within 2 hours after taking oral antibiotics, nor to drink fruit juice.

　　1. Western medicine treatment for gastrointestinal infection in SARS

　　During treatment, the focus should be on the main symptoms of SARS for ribavirin antiviral treatment, azithromycin or levofloxacin for infection prevention treatment, and non-invasive mechanical ventilation when necessary. The treatment of diarrhea is mainly symptomatic, attention should be paid to nutritional support to improve immunity and maintain electrolyte balance, and the abuse of antibiotics should be avoided. The timely control and improvement of diarrhea is an important link for the overall recovery of the disease. In the middle and late stages of SARS cases, especially those receiving unconventional doses of hormone treatment, gastrointestinal bleeding has also been reported frequently. For gastrointestinal complications, our experience is that: for those with diarrhea, oral gastrointestinal mucosal protective agents (such as double octahedral montmorillonite) can effectively control symptoms and have no side effects; for those using high doses of hormones, routine oral acid-suppressing drugs can prevent gastrointestinal bleeding with satisfactory results. The patient's feces should be strictly disinfected.

　　2. Traditional Chinese medicine treatment for gastrointestinal infection in SARS

　　SARS is 'Wind-heat' in warm diseases, and it is recommended to use honeysuckle, Forsythia, Platycodon grandiflorus, Lophatherum gracile, Dahuangzi, Lugen, Jingjie, Bohe, Sangye, and raw licorice as the main prescription, and add other drugs according to symptoms.

　　According to the advice of traditional Chinese medicine practitioners, those with severe throat pain should add Mabu or Yuan Shen, those with headache should add Chuanxiong and Baizhi, those with body pain should add Qianghuo and Chuanxiong, those with severe cough should add Xingren and Zhubei, those with a lot of yellow phlegm should add Huangqin and Maidong, those with severe fever should add Huangqin and Ge Gen, those with stomach bloating and no desire to eat should add Chenpi and Houpu, those with chest stuffiness and difficulty in breathing should add Zhishili and Yujin, and those with severe thirst should add Maidong and Tianhuafen.

　　3. Prognosis

　　This is a self-limiting disease, most patients are relieved or cured after comprehensive treatment. The symptoms of gastrointestinal infection also disappear accordingly.