People are kind, I speak like a doctor epidemiologist: wearing masks on the street and in the subway is not good, but harmful.
Why: the mask is not designed to be worn during physical activity (fast walking on the street)
When you wear a mask, you have hypoxia and forced (enhanced) breathing - the air, deforming the mask, jumps through its edges.
Then, entering the room where people are already and you can actually get infected, you continue to breathe for a while instead of the nose - mouth through these gaps.
As a result, you will get pneumonia instead of flu with nasopharyngitis and tracheitis - because the virus will jump through the upper respiratory tract.
And primary influenza pneumonia - in a large percentage of cases is fatal, unlike inflammation of the upper respiratory tract.