It is generally believed that viruses are found mainly in the feces, intestinal contents, intestinal epithelial cells and respiratory epithelial cells of infected animals and cause symptoms such as diarrhea and respiratory tract infections. About 10-30% of upper respiratory tract infections in the population are caused by coronaviruses, which are the 2nd leading cause of the common cold. Coronaviruses are sensitive to temperature changes and occur mainly in winter and early spring, and can be spread in two ways: i. Respiratory transmission Mainly through direct contact and droplet transmission, when the patient exhales, coughs or sneezes, the droplets spewed out land on other people and then enter the body through the mucous membranes of the eyes, mouth and nose. Second, contact transmission There is also the transmission of respiratory secretions or excretions, which is due to contact with daily necessities contaminated by the patient’s secretions or excretions, such as towels, tableware, telephones, etc., and then the virus enters the infected person’s body through the mucous membranes of the eyes, mouth, and nasal cavity, causing infection. However, respiratory transmission is limited to the area around the source of infection, and its infectious ability is limited for brief contacts between people in public places, so only close contacts around the source of infection may be infected, such as family members, patients and health care workers with higher infectivity. In addition, a study published in bioRxiv on January 30, 2020 concluded that novel coronaviruses have the potential to be transmitted through the digestive tract, and more epidemiological studies are needed to focus on this aspect. The best way to prevent transmission through the digestive tract is to wash your hands frequently, develop the habit of washing your hands before and after meals, and try not to eat or minimize raw and cold foods. How the coronavirus is infected The virus infects humans through respiratory or contact transmission, first destroying the body’s natural immune system’s first line of defense, followed by massive replication in the lungs, directly causing inflammation and necrosis of lung tissue, while the body’s immune system lymphocyte infiltration, inflammatory cell aggregation, the release of a large number of inflammatory cytokines, further aggravating the lung histopathological changes (including alveolar cell necrosis, decidualization, alveolar capillary congestion, hyaline changes, etc.). The virus continues to replicate, causing the patient’s condition to change and progressively worsen. During the onset and progression of the disease, the patient excretes a large amount of virus from the respiratory tract, which is highly infectious. A series of manifestations such as respiratory distress and lung damage also occur. Source: Dr. You Lai Reference Wang Fusheng, Xu Dongping. Study on the characteristics and pathogenic mechanism of SARS coronavirus [J]. Infectious disease information,2003(2):67-68. Li Yi,Sun Huinan. Transmission and protection of Middle East respiratory syndrome coronavirus[J]. Chinese Journal of Clinical Physicians,2015(9):9-11.