If I follow your argument the fever screening will get those infected with virus that tend to cause a higher fever than other virus. As we control those cases the others go on to reproduce and so the population of the virus then mutates to not causing the fever. Is that the basis position?
Yes.
If so, that seems to suggest how each person reacts to the infection is the same rather than the virus being the same but people reacting to it differently. If so, we will miss those who don’t respond to the infection with a fever (are as strong of a fever) but that should not create any environmental pressure to select for a low fever version of the virus.
Yes. The relevant thing is how much of the variance in fever is caused by mutations in the virus, versus being caused by differences between people. If people vary more in whether they have a fever than the virus varies in whether it causes a fever, this would weaken the evolutionary pressure; if they vary enough more, then my prediction of declining fever-screening effectiveness will be wrong.
Yes.
Yes. The relevant thing is how much of the variance in fever is caused by mutations in the virus, versus being caused by differences between people. If people vary more in whether they have a fever than the virus varies in whether it causes a fever, this would weaken the evolutionary pressure; if they vary enough more, then my prediction of declining fever-screening effectiveness will be wrong.