Unlike a bio-virus that has evolved for a billion years across all the niches of our ecosystems, when AI "escapes the lab" it's entirely confined to man-made infrastructure, it's not going to infect a flock of migrating birds and hop to the other hemisphere, it's going to be in systems we built, mostly within the past 30 years or less, mostly in the past 30 months for the powerful ones.
When AI starts demonstrating "copying itself" through DNA encoding infecting living beings without killing them (too quickly), and/or "running" on something more ubiquitous than massive data-center hardware, that's when it's over.