Capillary bronchitis, or acute infectious bronchitis, occurs mainly in infants and young children under 2 years of age, and is most common in infants under 6 months of age; it can occur throughout the year, but is most common in winter and spring, and is characterized clinically by runny nose, cough, paroxysmal wheezing, shortness of breath, inspiratory depression of the chest wall (trigeminal sign), prolonged expiratory phase on auscultation, audible croup, and fine wet bronchioles of 75-300 nm. The acute inflammation, mucosal edema, epithelial cell necrosis, and increased mucus secretion, leading to narrowing and obstruction of the bronchioles, is the pathological basis of the disease. The disease is self-limiting, but there is a high mortality rate in infants <6 months of age and at high risk. I. What causes capillary bronchitis. The common causes of capillary bronchitis are viral infections, respiratory syncytial virus, parainfluenza virus, adenovirus, influenza virus, enterovirus, rhinovirus, human metapneumovirus, and boca virus. In addition, Mycoplasma pneumoniae and Chlamydia pneumoniae infections can also cause capillary bronchitis. Early symptoms of viral upper respiratory tract infection in capillary bronchitis include nasal catarrh, cough, mostly feverless, but also low to moderate fever (where >39°C high fever is uncommon), which progresses rapidly after 1-2 d, with paroxysmal cough, wheezing, coughing and dyspnea in 3-4 d, and cyanosis in severe cases, reaching a peak of disease in 5-7 d. Other common symptoms include vomiting, irritability, irritability, decreased feeding, and apnea in small infants <3 months of age. Clinical examination often shows increased respiratory rate, prolonged expiratory phase, audible croup and fine wet rales. In severe cases, cyanosis, tachycardia, dehydration, inspiratory depression of the chest wall (triple concave sign) and nasal flapping may be present. Third, how to prevent capillary bronchitis. 1, chronic lung disease, premature infants (<32 weeks) or congenital heart disease and other high-risk children can be given palivizumab prevention; from the high season of RSV infection in November, 15mg per kg of body weight intramuscular injection of RSV F protein monoclonal antibody for 5 months, can reduce the hospitalization rate of RSV infection 39%-78% . Hand washing is the most important measure to prevent nosocomial transmission of RSV: wash hands before and after direct contact with the child, after touching objects adjacent to the child, and after removing gloves. 3. Infants and children should avoid exposure to crowded or passive smoking environments. 4. Breastfeeding is advocated. 4. Which infants are prone to severe capillary bronchitis. Premature infants (<37 weeks of gestation), low birth weight infants, infants younger than 12 weeks of age, infants with chronic lung disease, cystic fibrosis, congenital airway malformations, pharyngeal dysfunction, left-to-right shunt congenital heart disease, neuromuscular disease, immune deficiency, Down syndrome, etc. V. How to treat and care for capillary bronchitis. 1.Ensure unobstructed airway and adequate oxygen supply: In severe cases, oxygen or mechanical ventilation treatment is required. 2, to ensure adequate carbohydrate supply: if the child can normally eat breast milk, should be encouraged to continue breastfeeding, if the child's respiratory rate is greater than 60 times / min, and respiratory secretions, easy to occur spitting choking milk resulting in missuction can be considered nasogastric tube nutritional intake, if necessary, intravenous nutrition. 3, drug therapy: commonly used drugs are: (1), bronchodilators: β2 agonists: can be experimental nebulized inhalation of β2 agonists or the joint application of M-blockers, especially when there are allergic diseases, such as asthma, allergic rhinitis and other diseases family history. (2), glucocorticoids: nebulized inhalation glucocorticoid therapy is often chosen, and systemic glucocorticoid therapy can be used for more severe conditions. (3), 3% hypertonic saline nebulized inhalation can be tried (4), antibacterial drugs: consider the combination of bacterial infection, or mycoplasma, chlamydia infection when used. (5), sedative injection of human immunoglobulin: can be tried in more serious cases, especially in children with low immunity. The prognosis of capillary bronchitis. The vast majority of children with capillary bronchitis are able to recover completely without sequelae. Mechanical ventilation is required in 3-7% of hospitalized children. The majority of deaths due to capillary bronchitis occur in children younger than 6 months of age and in children with co-morbid cardiopulmonary disease. Approximately 34%-50% of children with capillary bronchitis will later develop airway hyperresponsiveness, such as recurrent cough, wheezing, and asthma.