(CNN) -- The deadliest outbreak of Ebola virus on record has sparked fears that the killer virus could spread from west Africa to other regions and continents.
The outbreak began with just a handful of cases in Guinea in March. Since then, there have been 814 confirmed cases and another 387 probable or suspected across that country, Sierra Leone and Liberia,according to the World Health Organization.
Some 672 people of the 1,201 total confirmed and possible infections have died, which equates to a 55% mortality rate, reports WHO as of July 23. (There have been 456 confirmed deaths due to Ebola.)
The WHO says "drastic action is needed" to contain Ebola, warning that previously undetected chains of transmission is boosting the numbers of sick and increasing the chances that the disease spreads from Africa.
"This epidemic is without precedent," said Bart Janssens, director of operations for Médecins Sans Frontières, also known as Doctors Without Borders. "It's absolutely not under control, and the situation keeps worsening... There are many places where people are infected, but we don't know about it."
The Ebola outbreak has been centered in Guinea, Sierra Leone and Liberia, where authorities have been working to contain the virus.
In Liberia, President Ellen Johnson Sirleaf announced Wednesday that, "without exceptions, all schools are ordered closed pending further directive from the Ministry of Education." She also declared Friday a non-working day "to be used for the disinfection and chlorination of all public facilities."
On the same day, the Peace Corps said it was temporarily removing its 340 volunteers from Liberia, Sierra Leone and Guinea due to the outbreak.
The announcement comes as two Peace Corps volunteers were isolated after coming in contact with someone who ended up dying of Ebola, a spokeswoman for the group said. She said these two Americans "are not symptomatic," and the Peace Corps will work to return them to the United States once they get medical clearance to travel.
Concerns about Ebola aren't confined to those three countries.
Last week, a Liberian government official who had contracted the virus died in isolation at a hospital in Lagos, Nigeria.
Patrick Sawyer, a naturalized American citizen who worked in Liberia, flew to Nigeria intending to attend a conference. After exhibiting symptoms upon arrival July 20, he was hospitalized and died on July 25. He's the first American to die in the outbreak, though two other U.S. aid workers in Liberia have contracted Ebola and are being treated.
And the UK government convened an emergency meeting to discuss the threat of Ebola to Britain, even though no case has been reported there. Officials discussed what measures could be taken if UK nationals in west Africa should become infected, Foreign Secretary Philip Hammond said.