After the apex of infection how long will it take to see numbers reducing?

[AbsentmindedWoman]

I'm shit at maths. How do the various models predict that rates of covid 19 infection will begin to slacken and reduce after the apex?

I'm being dim but why is it thought that rates reach a high point and then start to diminish - kind of in a 'mountain' shape with a sharp peak, rather than keep inclining (albeit at a very slow pace) or a 'table' shape where the rate maintains itself but doesn't keep sharply spiking?

Is the modelling based on social distancing working so the explosion of exponential growth slows quite dramatically? What other factors?

Can anyone explain in very simple terms to a maths dunce?

It really depends on how many people continue to catch it and pass it around.
I'd imagine it will be a slow decline, as people will continue to catch it but at a reduced rate, and those who have already caught it will start to show symptoms.
That said, if social distancing is having a good effect then there should be a very noticeable effect.

Most models I've seen show the total numbers of those infected or died, so there won't be a decline in that case, the line will just be a little less "steep" once new cases start decreasing.

We also have the difficulty that testing is not very rigorous here, so numbers of infected are almost meaningless. The numbers of deaths are a much better measure, and these are about four weeks behind the point of infection- so it will take four weeks after infection rates slow for the death rate to decrease.