Can saliva be used instead of a throat swab? Many people do not understand this question, including some medical professionals who cannot say why. In this popular scientific examination of the coronavirus nucleic acid amplification test, why a throat swab or nasal swab test is needed.

A pharyngeal swab or nasal swab is a method of wiping the posterior pharyngeal or nasal wall with a cotton swab as a test material for pathogenic microorganisms. Pathogenic microorganisms include:viruses, bacteria, mycoplasmas, chlamydia,Rapid antigen nasal swab parasites, and other microscopic organisms that cause disease. C. neoformans is a single-stranded RNA virus with small particles and few gene fragments. It cannot replicate itself, so it needs to rely on the host's genetic material replication system to produce new viruses. Because New Crown Pneumonia carries fewer base pairs of genes, mutation of a single base pair, or recombination of base pairs, produces a new mutant. Therefore, C. neoformans is a highly unstable virus. Since it has been recognized by humans, many mutant strains have appeared and have become increasingly infectious. Certainly, pathogenicity seems to be waning. C. neoformans is mainly transmitted by respiratory droplets, i.e., C. neoformans enters human cells by binding to a protein called ACE2 in respiratory epithelial cells, which are widely distributed in the respiratory tract, e.g., nasal mucosal epithelium, pharyngeal mucosal epithelium, and alveolar epithelial cells. In the early stage, the binding of C. neoformans to alveolar epithelial cells is high, and the body's main immune response is concentrated in the lungs. As a result, the early stages of the development of neococcal pneumonia are mainly exudative lesions in the lungs, which show imaging changes of ground-glass-like lung shadows, and then gradually progress to solid lung lesions. Of course, due to the body's own immune response, it can also cause damage to other parts of the body.

After invading the lungs, the virus is synthesized in large quantities in the lung epithelial cells. As sputum flows out of the body, it stays briefly in the pharynx, where some sputum viruses are contaminated in the posterior pharyngeal wall due to its non-smoothness. Most of the sputum is mixed in the mouth and spit out of the body. Therefore, virus detection is favored if sputum is obtained from deeper layers. However, in most cases, even in cases, the saliva that is spat out of the body is actually saliva from the mouth, which is produced by the parotid or sublingual or submandibular glands. In addition, in case of senility and fatigue from coughing, only spit is produced. Due to the low viral content of saliva, there is a low rate of positive viral detection. In conclusion, saliva is not suitable for the detection of coronavirus nucleic acids.

The pathogenic pattern of neocoronavirus pneumonia after mutation to omicron strain infection is mainly characterized by influenza-like symptoms, i.e., fever, sore throat, pharyngitis, cough, headache, nasal congestion, and muscle aches and pains, and there are few cases of lung shadowing on imaging. This suggests that the mutant neocoronary pneumonia is mainly concentrated in the nasal cavity, pharynx, trachea and bronchi. Nasal and pharyngeal swabs were collected for positive viral nucleic acid testing at a high rate.