There is a lot of misinformation about virus infectivity. When a cell is infected, it is turned into a 'virus factory'. It starts to make copies of virus. It also starts to make a large number of the components that are assembled within the cell to make a functional virus. Each one needs 1 of this, 12 of that etc and this continues until the cell 'lyses' =breaks apart releasing whatever is in the cellular envelope. .
Think like a car factory = 1 engines, 4 tires, 2 head lights etc. - a car with 3 tires, or one head light etc is not functional.
So covid has steadily evolved to create all it's sub components in the exact ratio to make the maximum number of virus particles before the shift is over = cell breaks and all the workers go home.
They call this the 'viral kinetics' and the maximisation explains the speed of spread.
In theory 1 particle can infect, but in practice it can take more due the the number of particles missing parts. The optimisation that has occurred in the past 2 years has gradually increased the rate of production of viruses as well as decreased the number of broken viruses created until the cell breaks open = increases the chance of getting the disease with only 1 particle. In practice there are usually multiple particles in a tiny blob of exhaled saliva.
Then we get an infection. The virus starts to breed - the innate immune system is ready 24/7 to destroy these, but we have a low level of innate immunity. The next stage is the adaptive immune system - have we had this before - if yes start the adaptive response. In 5-10 days the adaptive response starts to suppress the infection and get the upper hand. If we have not had this before = 3-5 weeks.
Vaccination and boosting gets our adaptive system ready with signals we have fought this before and this is why vaccinated people get a less severe infection. Paxlovid introduces 'left hand threads' into the nuts and bolts of viral reproduction and suppresses infection and give the adaptive system a leg up.
There are these 'tubes about it
https://www.youtube.com/results?search_query=paxlovid+mechan...