That's not the only way for a virus to spread beyond the facility, and most viruses in a lab for animals are viruses that cannot transmit to humans anyway.
Just the fact that it can be transmit to humans means the research needs to be in bio safety conditions, in the conditions it's bio safety level 3 lab as a requirement.
Ya, when the consequences of accidental screwup could mean the deaths of millions then how much risk are you willing to put up with??
Are you familiar with the track records of these companies making drugs and vaccines for viruses??
Let's say it's not good under strict conditions, what are you going to expect from people who are used to working with viruses that typically only infect animals?
What's worse, let's say the virus starts out, as not being serious, it is possible, though equally unlikely, that the virus could mutate from the wild to become more virulent... But it was all from an "accident" that they didn't realize they caused.
There's a certain level of risk that is simply unacceptable, that's why there's legislation and standards set to ensure that the work can be done with minimal risk beyond the lab.
What kind of extra risks do you feel should be acceptable while working with viruses and mutations that can cross infect between animals and people with no vaccine available??
Like, if the lab was studying airborne Ebola from a hospitals general bathroom, how concerned would you be?
I'm just curious at what point this nonchalance would shift into modest concern?