Why is it easier to catch respiratory infectious diseases including influenza in winter? Recently, a study published by the research team of Massachusetts Eye and Ear Hospital in the United States showed that the virus that invades the nose and causes upper respiratory tract infection will be cleared by the immune reaction in the nose, but this immune defense effect will be weakened with the decrease of temperature. The research team first collected three common cold viruses (one coronavirus and two rhinoviruses) exposed to the cells and tissues of the nasal cavity from patients and healthy volunteers who were ready for surgery, and then tested the immune response. Then the healthy volunteers were taken out of the room with a room temperature of about 23 ℃ and spent 15 minutes outdoors at 4.4 ℃. As a result, the temperature in the nasal cavity of these people decreased by about 5 ℃. Applying this temperature reduction to the nasal tissue, it was found that the human immune response had changed, and the release rate of extracellular vesicles (substances that attack and remove viruses and inhibit infection) decreased by nearly 42%, and the antiviral effect of extracellular vesicles also decreased. The researchers said that the above research revealed the fact that the biological root cause of the seasonal change in the prevalence of respiratory infectious diseases is the reduction of resistance due to the cold stimulation and the lower temperature of the nose in the cold environment. It can be seen that wearing masks in winter is not only to prevent the invasion of pathogenic microorganisms such as bacteria and viruses, as well as atmospheric pollutants such as haze, but also plays a very important role in keeping the respiratory tract warm (while moisturizing and humidifying) with the nose as the starting point, and improving the immunity and disease resistance of the respiratory tract. (Xinhua News Agency)