[reuben_scratton]

You must know that virologists routinely "serial passage" viruses through animal hosts? Evolving a candidate virus "through multiple, probably dozens of hosts" is what virology labs do.

And lab leaks happen All The Time. SARS-1 escaped labs on six separate occasions.

[bayesian_horse]

Serial passage actually weakens a Virus because this kind of evolution selects for properties that aren't useful for transmission outside the lab. And virulence usually decreases as well. Animal studies of this nature just don't have the numerical power to modify such properties intentionally.