The quarantine applies to medical workers who enter the US through John F. Kennedy International Airport in New York and Newark Liberty International Airport in New Jersey after treating Ebola patients in West Africa.

New York and New Jersey announced the quarantine on Friday, a day after a doctor tested positive for Ebola in New York City. Craig Spencer, 33, had treated Ebola victims in Guinea for a month under the auspices of Doctors without Borders.

Spencer is the fourth person to test positive for the virus in the United States. He is currently undergoing treatment in isolation at Bellevue Hospital Center (pictured above) in New York City.

"Voluntary quarantine is almost an oxymoron," New York Governor Andrew Cuomo said on Friday. "We've seen what happens…You ride a subway. You ride a bus. You could infect hundreds of people."

A female healthcare worker has already been quarantined under the new provision. She entered the US through Newark after treating Ebola patients in West Africa. Although she didn't initially exhibit Ebola symptoms, she started running a fever Friday evening. She is now in isolation at University Hospital in Newark.

Federal quarantine considered

The US federal government is considering a nationwide quarantine on healthcare workers who have treated Ebola patients in West Africa, according to Tom Skinner, a spokesman for the Center for Disease Control and Prevention (CDC).

Travelers arriving in the US from Guinea, Sierra Leone and Liberia are currently being routed through five airports that are screening for Ebola infection. The three West African nations are the worst hit by the virus.

But opposition Republican lawmakers are calling for tougher measures, including a travel ban against Guinea, Liberia and Sierra Leone. The White House has rejected a travel ban, saying it would likely make the situation worse.

Meanwhile, a US nurse has been declared Ebola free and released from hospital in Maryland. Nina Pham had fallen ill after treating a Liberian man who died of the virus in Dallas, Texas. Her colleague, Amber Vinson, no longer has detectable levels of the virus. But no date has been set for Vinson's release.

slk/mg (AFP, Reuters)