Speed limits are not put into effect because of clear and present danger. There is arbitrary element to them. In fact, there are places with no maximum speed limit. It’s just the way it is. When rules are made, the creators care of some ideas and arbitrate the rest. Going 57 mph is on different the 55.
Coronavirus, flu, Ebola, HIV, are not the reasons for mandatory health measures. Wide spread disease is. The word is ‘epidemic’.