The infections on your current life give you lives - it's not that if you infect 6 people you get 6 lives, but that if you infect someone on your current life, you can respawn.

ie. if you infect someone then die, you respawn, and then infect someone again then die again, you can respawn again
however if you infect 100 people then die, you respawn but then if you don't infect someone again after respawning and die again, then bye bye eternal zombie

The infections on your current life give you lives - it's not that if you infect 6 people you get 6 lives, but that if you infect someone on your current life, you can respawn. ie. if you infect someone then die, you respawn, and then infect someone again then die again, you can respawn again however if you infect 100 people then die, you respawn but then if you don't infect someone again after respawning and die again, then bye bye eternal zombie