What you do need to realize is are a few things. When somebody with an STD enters the country but has sex with nobody, nobody will get infected. When somebody with corona comes in, the story is different.
What is true is that the corona virus is indeed not even half as destructive as the media makes us believe, however the virus did already kill loads of people worldwide in a short time and some people have spent some time on the intensive care.
What is the difference between corona and the regular cold/flu... It's new, since the regular cold can be just as deadly, but as the virus causing that is old our bodies can resist it more. What is true however is that closing borders and locking countries up, like what happens now all over the world is not gonna help. In fact, most likely the only entity benefiting from that is the virus itself, and that is bitter irony.