Common Cold and Flu

Most of the causative agents of the common cold are viruses. The respiratory system consists of an air conduction portion and a respiratory portion. The direct initiating factor of the common cold is low temperature, especially relative coldness. When people feel cold or chilly, vascular constriction around the inlet area of air occurs, resulting in a reduction of mucus secretion containing various antiviral soluble mediators and followed by an explosive increase in the nasal viral flora. A relatively low temperature and dryness are good conditions for viral proliferation and invasion to the body. The first symptom of the common cold is usually a runny nose, followed by a sore throat and/or systemic fever. Acute symptoms of the common cold are usually terminated within 3 days, at the longest 5~7 days. The mortality rate of severe acute respiratory syndrome (SARS) has reached around 10%. A novel swine-origin influenza A (H1N1) virus caused the occurrence of more than 130,000 patients and dead cases of more than 800 people. H5N1 avian influenza showed an extremely high mortality rate, even though its infectivity is low. A new serotype of AI (H7N9) has appeared in some areas of China. Vitamin C can prevent the onset of a cold. Vitamin C can even prevent influenza virus from spreading down from the upper respiratory tract to the lower one. In addition, levels of interferon (IFN) in the bronchoalveolar lavage (BAL) fluid are markedly low in vitamin C-insufficient mice. Inflammatory cells are markedly increased in BAL fluid, providing the immunological evidences that daily supplementation of high-dose vitamin C can prevent influenza infection and that, in extreme case, it can save the life.