The Centers for Disease Control and Prevention said Monday that the risk of Ebola spreading to the United States was low, but it nevertheless issued a Level 2 health alert, advising U.S. health workers to be vigilant.

The largest outbreak of the Ebola virus on record has spread across the West African nations of Guinea, Sierra Leone and Liberia since first detected in March, with more than 670 deaths, according to the CDC.

Two Americans working in Liberia were diagnosed with the virus last week. That raised fears that the virus could be spread to the United States by those traveling from the region.

But the CDC played down the possibility. “The likelihood of this outbreak spreading outside of West Africa is low,” said Stephan Monroe, deputy director of the agency’s National Center for Emerging and Zoonotic Infectious Diseases. Still, he said in a teleconference with reporters, “the CDC has to be prepared for the remote possibility.”

The alert advised U.S. doctors to check patients’ travel histories to identify those who might have recently traveled to West Africa. The CDC also urged physicians to learn the symptoms of Ebola, which include fever and diarrhea, and the immediate treatment necessary if they suspect it. The agency warned travelers going to West Africa to avoid contact with bodily fluids or blood of anyone in the affected areas.

Kent Brantly, an American physician who was infected, is undergoing treatment at the isolation ward at ELWA Hospital in the Liberian capital of Monrovia. As director of the Ebola Consolidated Case Management Center run by Samaritan’s Purse, a Christian charity, in Monrovia, Brantly worked closely with Ebola patients.

His wife and two children had been living with him in Liberia but returned recently to the United States, and they are being watched closely for symptoms as a precaution.

Nancy Writebol, who worked with an international mission organization, also tested positive for the virus and is under surveillance. Both she and Brantly had been in the region providing medical humanitarian assistance before the outbreak.

Doctors Without Borders, which has more than 300 staff members responding to the outbreak, said its resources were stretched to the limit by the epidemic.

The fact that there is any risk, even if it is a low one, of the virus spreading to the United States should be a reminder that all countries have a vested interest in responding to the crisis in West Africa and working to protect global health security, said Monroe.

The Liberian government on Sunday closed most border crossings, restricted public gatherings and announced an increase of surveillance of travelers at entry and exit points in the country, including at the country’s main airport. The government adopted the stricter measures after a man was reported to have died of the virus in Nigeria.

Patrick Sawyer, a consultant for the Liberian Ministry of Finance, was confirmed to have died from Ebola infection on Friday. He had been quarantined by Ni­ger­ian authorities when he arrived at Lagos Airport earlier last week.

(The Washington Post)

Wade Williams, an editor and reporter at the Liberian online magazine Front Page Africa, said that Sawyer’s sister had recently died of Ebola, and Sawyer had taken her to hospital.

Williams met both of the Americans infected nearly a month ago when she filmed the burial of Ebola patients at ELWA Hospital. Writebol, she said, had a white body bag opened so a family could say a last goodbye to their deceased loved one, and she reminded local colleagues who were about to remove their protective gear to go through decontamination.

On Saturday, Samuel Brisbane, a senior Liberian doctor who had devoted himself to treating Ebola patients, was the first Liberian doctor to die of the virus in this outbreak.

Local health workers often lack adequate resources such as personal protective equipment and training despite being at risk, said Williams.

“I have a neighbor who is a nurse, and the government hasn’t even given nurses the gloves to protect themselves,” Williams said. “I told her: ‘If the government is not giving you protective gear, you don’t have to go to hospital.’ ”

Even in neighbouring Guinea, where cases have declined, Monroe likened the epidemic to a wildfire that can be spread again by a single spark.

“The response to this outbreak will be more a marathon than a sprint,” he said.