How often does this sort of thing happen? I'm guessing more than we think, either because we forget the news stories we read or because it isn't reported.
A while ago a researcher at the Univ. of Chicago died of the plague. Although most labs use a mutated form that can't get iron needed to reproduce, he had a medical condition that caused an excess of iron in his blood that might have yet the bacteria grow.
However, every year there's a few deaths in the US from the plague because it's present in a variety of animals. If you look worldwide, there's probably on the order of a thousand deaths annually.
Bubonic plague is known to be active in Colorado, I think there are a handful of cases each year
Also ask how much is this failed route procedures because organisms or viri of this variety won't continue without human sustainment which is prone to human failures...
Janet Parker was the last person to die of smallpox and, yes, she caught it in a lab [1].
[1]: https://whyy.org/segments/the-tragic-case-of-smallpoxs-final...
There was a COVID 19 lab leak in Taiwan about a year into the pandemic.
https://www.taiwannews.com.tw/news/4374289
Six errors contributed to this leak.