In recent media reports, you may have seen many articles comparing this new coronary pneumonia to the previous flu, but most of these articles fail to define these terms accurately. Today, Heartland Classroom will take a look at these respiratory diseases that are often encountered in daily life but are difficult to explain the fundamental differences. First, we need to understand the human respiratory tract: the human respiratory tract is divided into the upper respiratory tract and the lower respiratory tract, with the lower edge of the cartilage in the ring as the boundary. The upper respiratory tract starts from the external nostrils and includes the nasal cavity, pharynx and larynx; the lower respiratory tract ends at the alveoli and includes the trachea, bronchi and lungs. Upper respiratory tract infection is a general term for acute upper respiratory tract infections, mostly occurring in winter and spring, and can be small-scale epidemic. Most of these pathogens are widespread in nature and may also be carried by healthy people. When rain, cold, sudden climate change, overexertion, etc. can reduce the local defense function of the respiratory tract, which is exposed to or originally carried by the pathogens to multiply rapidly, resulting in the appearance of symptoms. Generally speaking, people with low immune function are prone to develop the disease, but even so, the disease is usually mild, short-lived, and self-healing. Inflammatory factors are involved in the onset of epithelial cell damage in the upper respiratory tract, resulting in vascular congestion and increased secretions in the upper respiratory mucosa, accompanied by plasma and mucus inflammatory exudates. Classification of upper respiratory tract: 1) common cold, 2) acute viral pharyngitis and laryngitis, 3) acute herpes pharyngitis, 4) acute pharyngeal conjunctivitis, 5) acute tonsillitis. Here we mainly talk about the common cold: narrowly defined as upper sensation, mostly caused by viral infection, also known as acute rhinitis or upper respiratory tract catarrh. The onset of the disease is rapid, mainly manifested as nasal symptoms, sneezing, nasal congestion, runny nose, etc. When the virus-induced inflammatory mediators lead to afferent nerve hypersensitivity in the upper respiratory tract, cough, dry throat and itchy throat will also appear. In severe cases, there will be fever, mild chills and headache. The disease is usually cured in 5-7 days, but may be prolonged in cases with complications.