According to the World Health Organization (WHO) two cases of ebola fever have been confirmed in Liberia, which means that the highly contagious virus has started to spread from Guinea across West Africa. 

WHO offers more details on their website: 

As of 29 March, seven clinical samples, all from adult patients from Foya district, Lofa County, have been tested by PCR using Ebola Zaire virus primers by the mobile laboratory of the Institut Pasteur (IP) Dakar in Conakry. Two of those samples have tested positive for the ebolavirus. There have been 2 deaths among the suspected cases; a 35 year old woman who died on 21 March tested positive for ebolavirus while a male patient who died on 27 March tested negative.  Foya remains the only district in Liberia that has reported confirmed or suspected cases of EHF.  As of 26 March, Liberia had 27 contacts under medical follow-up. 

The woman who died was married to a Guinean man and had just returned from a trip to that country, where she contracted the virus. The second person with a confirmed case of Ebola is the woman's sister. Liberia's Health Minister Walter Gwenigale told Al Jazeera that she is alive and quarantined, but refused to divulge more information "because we don't want to cause panic." According to Reuters, eleven deaths in Sierra Leone and Liberia are also suspected of having been caused by Ebola. 

Officials suspect that the virus was transferred to people in Guinea via fruit bats, a delicacy in parts of the country. The consumption and sale of bats has since been made illegal. 

There's no cure for or vaccine against the virus, which was first identified in Sudan and Zaire in 1976 and is "one of the most virulent viral diseases known to humankind," according to WHO, which adds: 

The Ebola virus is transmitted by direct contact with the blood, body fluids and tissues of infected persons. Transmission of the Ebola virus has also occurred by handling sick or dead infected wild animals (chimpanzees, gorillas, monkeys, forest antelope, fruit bats).

Though WHO has said it "does not recommend that any travel or trade restrictions be applied to Liberia, Guinea or Sierra Leone based on the current information available for this event," Senegal has closed its border with Guinea as a preventative measure. "When it used to be only in the south of Guinea, we didn't do anything special. But now that it's reached [Guinea's capital] Conakry, we believe it's safer to close our borders," said Senegal's Health Minister Awa Marie Coll-Seck, adding "We have also closed all weekly markets, known as luma, in the south. And we're having some discussions with religious leaders regarding big religious events." A Senegalese performing artist also cancelled a concert in Conakry, telling reporters it didn't seem wise to bring large crowds of people together during the outbreak.

Meanwhile, WHO officials continue to record deaths and cases of the virus in Guinea: 

Where health care workers are also at risk: