First we need to know how the virus infects patients.
For a virus to enter a cell, the cell must have its corresponding receptor (Receptor). For example, the common receptor for HIV is CD4 protein, which is usually on the surface of immune cells in the blood, so HIV can be transmitted through the blood without worrying about air transmission.
The new coronavirus receptor, like SARS, is angiotensin-converting enzyme 2 (ACE2). This means that for the virus to infect humans, it must first contact cells with the enzyme to complete receptor binding.
And we happen to have a lot of these cells exposed to the air-the mucosa.
The significance of the mucosa is to secrete mucus and keep it moist.
There are a lot of mucosal cells in our lips, eyelids, nasal cavity and oral cavity. When the virus contacts your oral mucosa in some way and binds with the receptor, the infection begins.
In order for you to understand what happened next, we have made a simplified rough process.
First, the envelope of the coronavirus fuses with the cell membrane, releasing viral genetic material—a single strand of RNA.
This RNA can be used directly as messenger RNA, tricking the ribosome in the cell to synthesize RNA replicase.
The RNA replicase will generate the negative RNA strand based on the viral RNA. This negative strand will continue to generate more viral RAN fragments and positive RNA strands with the replicase. These different RNA fragments will generate more different viral protein structures with the ribosome. .
Finally, the protein coat and RNA combine to form new coronavirus particles, which are secreted out of the cell through the Golgi apparatus and infect new cells.
Each infected cell produces thousands of new virus particles that spread to the trachea, bronchi, and eventually reach the alveoli, causing pneumonia.
After the infection is complete, transmission is not difficult. The saliva secreted by your three pairs of salivary glands will be mixed with respiratory secretions from the throat and other parts, allowing the virus-laden saliva to spread into the air with your sneeze and cough, and to contact other people's mucosa.
Mucosal infections and droplets spread, which is why coronaviruses spread so easily.
On December 8, 2019, a patient from the South China Seafood Market was admitted to the hospital due to fever, cough, and difficulty breathing for 7 days. Five days later, he had not been to a seafood market and his wife was admitted to the hospital with pneumonia for unknown reasons.
On January 1, 2020, the South China Seafood Market was closed. On January 2, 41 patients with new pneumonia were diagnosed.
At this time, the citizens who welcomed the Spring Festival did not know that a plague that could affect tens of thousands of people had begun.
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