US federal health officials have revamped guidelines for doctors and nurses returning to the country from treating Ebola patients in West Africa, stopping short of controversial mandatory quarantines being imposed by some US states.

On Monday, Thomas Frieden, director of the US Centers for Disease Control and Prevention (CDC), called for voluntary home quarantine for people at the highest risk for Ebola infection but said most medical workers returning from the three countries at the centre of the epidemic would require daily monitoring without isolation.

New York and New Jersey are among the states imposing mandatory quarantines on returning doctors and nurses amid fears of the virus spreading outside of West Africa, where it has killed nearly 5,000 people in the worst outbreak on record.

Also on Monday, Kaci Hickox, a US nurse who worked in West Africa with Ebola patients was released after being quarantined through the weekend in an isolation tent at a New Jersey hospital.

Under new CDC guidelines that spell out four risk categories, most healthcare workers returning from West Africa's Ebola hot zone would be considered to be at "some risk" for infection, while healthcare workers tending to Ebola patients at US facilities would be seen as "low but non-zero" risk.

Frieden said high-risk people include healthcare workers who suffer a needle stick while caring for an Ebola patient or who tend to a patient without protective gear. 

He said returning health workers at "some risk" would have their health monitored daily by a local health department official who would check their temperature, look for signs of fatigue and review their daily activity plans to determine what activity "makes sense for that individual, at that time."

Strict states

The Obama administration's new guidelines are not mandatory and states will have the right to put in place policies that are more strict.

President Barack Obama's spokesman, Josh Earnest, made clear on Monday that the White House was not thrilled that individual states had implemented quarantines viewed as unfair to returning healthcare workers, though he acknowledged the states' rights to set them.

"We want to make sure that whatever policies are put in place in this country to protect the American public do not serve as a disincentive to doctors and nurses from this country volunteering to travel to West Africa to treat Ebola patients," Earnest said.

Some US state officials, grappling with an unfamiliar public health threat, had called federal restrictions placed on people travelling from Ebola-affected countries insufficient to protect Americans and have imposed tougher measures.

The CDC's Frieden warned against turning doctors and nurses who are striving to tackle Ebola in West Africa before it spreads more widely into "pariahs".

With thousands already dead from Ebola in Liberia, Sierra Leone and Guinea, concerns are high in the US about stopping its spread.

Public health experts, the United Nations, medical charities and even the White House have denounced mandatory quarantines as scientifically unjustified and an obstacle to fighting the disease at its source in West Africa.

Source: Agencies