"The Plague and the Fire" is available on Kindle, so I'm rereading it. I came across something funny:
"[T]he Bills of Mortality had already recorded three cases of death by 'Pestilence', one of them in the out-parish of St Giles-in-the-Fields during December. This caused little concern, for London was rarely entirely free from plague, and an occasional case among the thousand of deaths from other diseases set out in the Bills could pass almost unnoticed. It was no more remarkable than a case of diphtheria would be today."
Wait, what? I've never even heard of a case of diphtheria. So I checked Wikipedia (reliable for something like this) and learned:
"In the United States, 57 cases were reported between 1980 and 2004."
So, just over two cases per year in the entire country, and that's just cases, not deaths. A case of diphtheria would definitely be remarkable!
"The Plague and the Fire" was first published in 1962, so diphtheria was common then, but disappeared within the next eighteen years. Modern medicine is quite amazing.