The immune system's response to a coronavirus attack

COVID-19 is not different from how influenza viruses attack the body. Therefore, the immune system has a predictable response to it.
A cascade of viral particles enters the body through the nose, eyes or mouth. Breathing carries some of these particles to the lower respiratory tract.
Here the spike proteins of the coronavirus, acting like a key, lock into epithelial cells. SARS-CoV-2 is able to stay undetected longer than many flu or coronaviruses.
Its spike proteins are able to gain entry by unlocking the ACE2 protein on the lung cells.In the case of SARS-CoV-2, the virus seems better at penetrating deeper.
The inflammation triggers a fluid build-up in the lungs. Apart from producing mucus and a runny nose to trap viral particles and prevent their ingress.
The fluids also contain the residue of a host of specialised cells — including T cells. These carpet bomb and damage many of the body’s own cells as well as the viral particles.
It is in expelling this fluid that a dry cough, characteristic of the coronavirus infection, begins. As more airsacs are infected, the lungs find it harder to extract oxygen from the air. And eventually, this aggravates breathlessness.