" There would therefore have been all the more delight at the birth of the first son William within less than a year of Margaret's death, tinged with more than a little anxiety, in view of the fateful words hic incepit pestis, 'here began plague', in the burial part of the register three months later. Just how close this dread flea-borne disease was to the Shakespeares can be guaged from the fact that their Henley Street neighbour Roger Green lost four of his children and town clerk Richard Symons three. One estimate suggests that the town lost around two hundred, or about fifteen per cent, of its population during this single outbreak. It is a sobering thought how much the world could have lost at this time by one ill-chanced flea-bite. "

― Ian Wilson , Shakespeare: The Evidence: Unlocking the Mysteries of the Man and His Work