A person who becomes ill with COVID-19 begins to infect others three to four days before the onset of symptoms (in rare cases, seven days), and he is most infectious two days before them and on the first day of illness. This was reported by the Deputy Director for Clinical and Analytical Work of the Central Research Institute of Epidemiology Professor Natalya Pshenichnaya.

The person who is sick remains contagious for five days after the onset of symptoms; later, the chance of infecting someone is small. The new coronavirus infection spreads mainly by airborne droplets, Pshenichnaya specified.

All present infections are most contagious during cough phase.

Here they effectively tell you that biggest issue is normally looking person without any temperature or coughing.

In nature it is very inefficient strategy. But if you want to make sure that virus will become very hard to stop and to filter out sick persons - it is ideal design.

It is also ideal as it make inefficient the subconscious behavior of distancing from someone who cough hard.