>>36622
They knew about it too and tried to deal. Mostly on Galenic basis. Galen lived through the Antonine Plague, treating many cases, and he left his notes to the posterity. How effective was his treatments? Who knows. How effective our "treatment"? They don't do much in hospitals, just put peeps, who tired out and can't breath by themselves anymore, onto ventilators, but they just sit around and wait patience to get better. At least Galen was concerned about the general physical well being of the people. Now they don't even advise "lose weight fatsos". Otherwise they try to prevent the spread with quarantine. I think that was also known practice in the antiquity.

>>36623
The risk is due to the unhealthy state of the heart and such - due to being fat, lazy and weak. The older these unhealthy people are, the weaker they are, the more likely they end up dead.
The low median age of the medieval is a little misguiding, the high mortality rate of children weighs a lot in that. Ofc many other conditions could ensure lower life expectancy, but peeps back then could live 60-80 fine.