The virus is causing the pneumonia (which literally means lung inflammation). Although it is possible to get a superimposed bacterial infection over the top of this (to be mildly flippant, double pneumonia) because the lungs aren’t clearing debris and another infection can take hold. But the damage is specifically from the effects of the virus
I think the question was whether the virus causes permanent damage in patients without pneumonia.
Edit: From the translated article, apparently yes:
> All of them were not severe cases, their illnesses were five to six weeks ago and they are considered to have recovered. But they can no longer dive. "The damage to the lungs is irreversible"
Pneumonia can scar the lungs, but COVID appears to be able to scar the lungs without causing Pneumonia. It interferes with hematic function (the ability of your blood to exchange oxygen) leading to the formation of ground glass bodies in the lungs. However, with most people now thought to get COVID asymptomatically, it is likely only a small percentage of the infected leave with permanent damage.
Basically what COVID-19 does is bind to receptors in the delicate tissue of your lung’s air sacs. This prevents oxygen from crossing the barrier into the bloodstream.
What makes it worse is that your own immune response, which comes to try and fight the virus, ends up causing more blockages.
What these articles are unclear about is why this is “permanent”. But a guess is that it’s like fibrosis where the tissue is permanently hardening — like layers and layers of hardening paint on the interior walls of your house.
The aggressiveness of your immune response might be a variable that explains why some people get this worse than others — just a guess.
Inflammation, like with so many things, seems to be a big factor. This might be what’s happening with all the heart problems, but again no one is sure about anything at this stage.