It was observed that the ordinary burials increased in number considerably

From A Journal of the Plague Year by Daniel Defoe.  

“This increase of the bills stood thus: the usual number of burials in a week, in the parishes of St Giles-in-the-Fields and St Andrew’s, Holborn, were from twelve to seventeen or nineteen each, few more or less; but from the time that the plague first began in St Giles’s parish, it was observed that the ordinary burials increased in number considerably. For example:—

     From December 27 to January 3   { St Giles’s          16

{ St Andrew’s      17 

 January 3  to    10                     { St Giles’s         12 

{ St Andrew’s     25 

January 10 to  17                       { St Giles’s         18 

{ St Andrew’s      28 

January 17 to 24                       { St Giles’s          23 

{ St Andrew’s     16 

January 24 to 31                       { St Giles’s          24 

{ St Andrew’s     15 

January 30 ” February 7           { St Giles’s          21 

{ St Andrew’s     23 

February 7 to 14                       { St Giles’s         24 

Parallels to today:

This is a very interesting one.  In 1665 they were immediately focused on Total All Causes Death Rate which is what we should have been doing all along.  We still do not pay too much attention to All Causes Death.  Instead we have distracted ourselves by focusing on test results (from tests which have been known to be unreliable since the beginning with too many false positives and negatives), hospitalizations, etc.  

By trying to anticipate whether there would be a hospital crunch (there wasn't) we focused on unreliable precursor measurements that would allow us, we thought, insight to what was coming in terms of hospitalizations.

In 1665 there were no hospitals to speak of, no testing, and little public health authority.  The public knew there was a problem not because people were ill but because the All Causes Death (as measured by burials) was materially higher than normal for the season.

In general, you never want to bo backwards to the healthcare conditions of yesteryear but in this instance, they had a clearer understanding of the reality of the plague than did any of the modern nations of the Covid-19.