(CNN) — Humanitarian agencies working in west Africa are stepping up precautions against the deadly Ebola virus as local and international health officials struggle to bring the outbreak under control. The Peace Corps announced Wednesday it was removing hundreds of its volunteers from the region.
The Peace Corps said 340 workers would temporarily leave Liberia, Sierra Leone and Guinea, the three countries primarily affected by the outbreak.
Two volunteers on the continent were isolated after coming in contact with someone who later died of the virus, a spokeswoman told CNN. They are not exhibiting Ebola symptoms, and will return to the United States when they receive medical clearance, she said.
“The agency has been and will continue to closely monitor the outbreak of the virus,” the Peace Corps said in a statement. “A determination on when volunteers can return will be made at a later date.”
Health officials have called this the deadliest Ebola outbreak in history.
As of July 23, the World Health Organization had confirmed more than 800 Ebola cases in the region, but suspects there have been many as 1,200 cases. WHO estimates 672 people have died.
Other aid organizations in the area are trying to protect their workers, too.
Two Americans working with Samaritan’s Purse who were infected with the deadly Ebola virus “have shown a slight improvement in the past 24 hours,” according to the evangelical Christian humanitarian agency.
Both remain in serious condition, the agency said.
Because of the uptick in Ebola cases in the region, Todd Shearer, a spokesman for Samaritan’s Purse, told CNN that the organization is evacuating nonessential staff out of Liberia. Serving in Mission also has recalled all nonessential personnel from Liberia, according to its website.
Dr. Kent Brantly, 33, who last lived in Fort Worth, Texas, and Nancy Writebol, who is from Charlotte, North Carolina, sought treatment for exposure to the virus last week. Both were caring for patients with Ebola in Monrovia, Liberia’s capital.
“We ask that people continue to pray for Kent and Nancy and all those who are affected by Ebola, and the tremendous group of doctors and nurses who are caring for them,” Samaritan’s Purse said in a statement.
Doctors and other medical staff are particularly vulnerable to the Ebola virus because it spreads through exposure to bodily fluids from the infected. It can also spread through contact with an object that has been contaminated by an infected person’s bodily fluids.
Brantly works with Samaritan’s Purse. He has been the medical director for the Ebola Consolidated Case Management Center in Monrovia, where he has been providing care for Ebola patients since October. After testing positive for the virus, Brantly went into treatment at ELWA Hospital.
Samaritan’s Purse has been working to evacuate him for better care, said Ken Isaacs, vice president of the agency. Unfortunately, emergency medical evacuation flights in the area are not equipped to handle the “intense isolation” required for an Ebola patient.
Brantly’s family had been with him in Liberia, according to the U.S. Centers for Disease Control and Prevention, but left for the United States before he became symptomatic; it is highly unlikely that his family members caught the virus from him, the CDC said. Out of an abundance of caution, they are on a 21-day fever watch, the CDC said.
“We have a strong family unit within a stronger faith community that has given us incredible support,” the Brantly family said in a statement Tuesday. “Kent remains very physically weak, but his spirit has been determined throughout this ordeal.”
Writebol works for Serving in Mission, or SIM. The missionary organization had teamed up with the staff from Samaritan’s Purse to help fight the Ebola outbreak when she got sick.
It is believed one of the local staff was infected with Ebola and came to work with the virus on July 21 and 22, Isaacs told CNN.
“We think it was in the scrub-down area where the disease was passed to both Nancy and Kent,” he said. That staff member died Thursday.
On Monday, the CDC issued an alert warning travelers to avoid hospitals with Ebola patients and funerals for those patients in Liberia, Sierra Leone and Guinea due to the outbreak. The United States is considering raising the alert to discourage “nonessential” travel to those three countries, a spokesman said.
Liberia has closed its schools and is advising residents to avoid public amusement and entertainment areas, President Ellen Johnson Sirleaf said Wednesday. Earlier this week the country closed its borders to try to contain the virus. Sirleaf has also declared Friday, August 1 a non-working day in order to sanitize all public areas.
“My fellow Liberians, Ebola is real. Ebola is contagious. And Ebola kills,” Sirleaf said. “All of us must all take extra measures announced by the Ministry of Health to keep ourselves safe. The government will do its part. But you must do yours.”
CNN’s Greg Botelho contributed to this report.