How do they know someone has died OF COVID without a post mortem?

Symptoms are a bit of a give away.

https://www.drugs.com/medical-answers/covid-19-symptoms-progress-death-3536264/

The mortality rate alone should not be considered a pointer as to the seriousness of the disease.  The security chief at the White House recently left hospital having taken several weeks to recover.

He is now without his left big toe and his right leg below the knee.

I am surprised given the ease of world travel and the history of infectious diseases, that anyone would suspect the coronavirus to be anything but an easily possible event.