My husband has a preexisting condition. Will a new insurance cover his expensis due to this condition or no?

Husband was diagnosed with Hepatitis C and resulting stage 4 liver disease two years ago. He wants to leave current job(insurance is currently Harvard Pilgrim)We are concerned that due to his serious preexisting condition a new employers insurance will not cover med care ociated with preexisting condition and he could actually die if that is the case! We need to know the law before he moves from one job to another.