I'm thinking house discovers the problem while conducting some experimental brain surgery, where the yeerk is knocked out by the annastesia, but the host isn;t completely. The host wakes up and explains everything.
One or two of the doctors observing the strange new disease try to escape/attack everyone and from that point they get two more links to the yeerks. With House's influence, he could have them put into solitary confinement for three days, and take what they know after.