Acute bronchiolitis is a common acute infection of the lower respiratory tract mainly in the bronchioles in infants and young children. It is only seen in infants and young children under 2 years old, mostly in infants aged 1 to 6 months. The onset is related to the anatomical characteristics of the bronchi at this age. The tiny lumen is easily obstructed by viscous secretions, edema and muscle contraction, and can cause emphysema or atelectasis. Its clinical symptoms are like pneumonia, and the wheezing is more obvious, characterized by obvious wheezing cough and hypoxia symptoms. It is difficult to find pure bronchiolitis that does not involve the alveoli and the alveolar wall in clinical practice, so it is considered a special type of pneumonia in China. In fact, it is different from pneumonia. This disease can be prevalent, and some people call it wheezing pneumonia. Various parts of China have called it: epidemic bronchiolitis (Guangxi), epidemic wheezing pneumonia (Zhejiang), pediatric wheezing pneumonia (Shanghai), epidemic asthma (Guangdong), epidemic asthma pneumonia (Jiangxi), etc. As for the epidemic asthmatic pneumonia that broke out in our country, it will be described separately.