Sick
Sam rarely got sick, but when he did, it was bad. Like, unable to move from out of his bed because it hurt too much, bad.
The few times it occurred, Bumblebee had been frantic with worry, constantly checking his vitals and bugging the gears out of Ratchet.
Thank Primus that the Allspark kept illnesses away from his charge now, because Bee knew that not every disease could be cured.
If he had lost Sam that way, or any way, well, not all sicknesses were physical, and Bee's spark would never have healed.