Patients are contagious only once the disease has progressed to the point they show symptoms, according to the World Health Organization. The swelling numbers prompted heads of state to cancel travel plans on Thursday to direct their full attention toward fighting the outbreak of the virus that has crippled parts of Liberia, Sierra Leone and Guinea and stirred palpable concerns that it will spread around the region and the world. President Ellen Johnson Sirleaf, who is skipping a summit of African leaders in Washington this week amid the crisis, also called for the closure of markets in an area near the borders with infected countries Guinea and Sierra Leone. Samaritan's Purse -- an international evangelical Christian humanitarian agency -- and the missionary group Serving in Mission have recalled all nonessential personnel from Liberia. In a statement released Wednesday, the Peace Corps said that 340 volunteers in the three affected countries were being evacuated and "a determination on when volunteers can return will be made at a later date." The BBC's West Africa correspondent Thomas Fessy says treatment facilities have reportedly been overwhelmed in the Liberian capital Monrovia. 2 infected Americans 
 
 Ebola spreads through the transmission of bodily fluids. "We join the families in prayers that they can come through this and become ... shining examples that, if care is taken, one can come out of this." Liberian President Ellen Johnson Sirleaf has told the Ministry of Health to consider quarantines in some areas and cremating bodies in an attempt to prevent further infection, according to Brown. The president also urged residents to avoid public amusement and entertainment areas, and set aside Friday "for the disinfection and chlorination of all public facilities." "My fellow Liberians, Ebola is real, Ebola is contagious and Ebola kills," she warned. Sirleaf said that security forces would enforce the new precautions taken a week after an American man of Liberian descent boarded a plane in Monrovia and flew to Nigeria, where authorities said he died of Ebola. Non-essential government workers will be sent home for 30 days and the army deployed to enforce the measures.
– The Peace Corps is evacuating its volunteers from the three nations in West Africa hit hard by the Ebola epidemic, reports CNN. The 340 Americans will be returning to the US from Liberia, Sierra Leone, and Guinea as the outbreak worsens. In fact, two Peace Corps workers must remain behind in isolation because they had contact with an infected person, though neither has shown symptoms, says the group. The move comes as health officials try to contain the disease to West Africa. Today, Liberia shut down all its schools, sent home non-essential government workers for three weeks, and dispatched troops to enforce quarantines in some communities, reports the BBC. "My fellow Liberians, Ebola is real, Ebola is contagious and Ebola kills," said President Ellen Johnson Sirleaf. "Denying that the disease exists is not doing your part, so keep yourselves and your loved ones safe." With 670 deaths and counting, the outbreak is now the largest in history, reports the AP. "This epidemic is without precedent," says the director of Doctors Without Borders. "It's absolutely not under control, and the situation keeps worsening."