Martin Furmansky chronicles the history of dangerous viruses escaping from labs. The bottom line:
Looking at the problem pragmatically, the question is not if such escapes will result in a major civilian outbreak, but rather what the pathogen will be and how such an escape may be contained, if indeed it can be contained at all.
Experiments that augment virulence and transmissibility of dangerous pathogens have been funded and performed, notably with the H5N1 avian influenza virus. The advisability of performing such experiments at all—particularly in laboratories placed at universities in heavily populated urban areas, where potentially exposed laboratory personnel are in daily contact with a multitude of susceptible and unaware citizens—is clearly in question.
If such manipulations should be allowed, it would seem prudent to conduct them in isolated laboratories where personnel are sequestered from the general public and must undergo a period of exit quarantine before re-entering civilian life. The historical record tells us it is not a matter of if but when ignoring such measures will cost health and even lives. Perhaps many lives.