Of visible, physical danger. Running into a burning building, towards gunfire, etc.
A virus that kills 0.1-0.5% of people it infects doesn't meet the threshold. Even if the rate of death is similar, the intimidation of being shot at or running into a fire takes an inner fortitude most don't possess. That's what makes those people heroes.
I greatly respect our nurses and doctors and so does most of the us, that's why we pay them so well. They're of great value and great people in general. But I don't view them as heroes.