U.S. health officials on Monday recommended little more than voluntary, at-home quarantine for travelers from West Africa who are at highest risk for coming down with Ebola, and symptom monitoring for those at lower risk.

The Centers for Disease Control and Prevention issued the updated guidance on Monday.

The CDC guidance comes after the governors of New York, New Jersey, Illinois and Maryland announced mandatory quarantines for medical workers returning from three West African countries plagued by the worst Ebola outbreak in world history.

Experts say the state actions are unnecessarily severe and will discourage health workers from going to West Africa to fight the epidemic. The CDC said travel restrictions could be ordered in certain cases, but voluntary quarantine is enough for those at highest risk.