The World Health Organization said Thursday it is sending 11,000 doses of Ebola vaccine and more than 100 experts to Guinea to address an Ebola outbreak in the West African nation.

Speaking in a virtual news conference from her headquarters in Brazzaville, Republic of Congo, WHO Africa Director Matshidiso Moeti said officials are also expecting an additional 8,600 doses of vaccine from the United States, for a total of nearly 20,000 shots. She expects them to arrive by Sunday and Ebola vaccinations to begin by Monday.

Health officials in Guinea declared an epidemic Sunday after three cases were detected in Gouecke, a rural community in N'Zerekore prefecture. At least one victim there has died. It is the first Ebola outbreak in Guinea since 2016 when a large one was brought under control.

Moeti said the WHO released $1.25 million to support the response in Guinea and to show its "readiness" in the neighboring countries of Cote d'Ivoire, Guinea-Bissau, Liberia, Mali, Senegal and Sierra Leone. She said the epicenter of the outbreak was in the border area, so the entire sub-region is on high alert.

Meanwhile, the WHO said there four confirmed Ebola cases in the Democratic Republic of Congo, including two deaths. The agency has around 20 experts supporting national and provincial health authorities in the DRC.

The United Nations announced it is releasing $15 million from its emergency relief fund to help fight the outbreaks in both Guinea and the DRC.

Ebola is an acute severe viral illness and is extremely lethal. It is characterized by sudden onset of fever, intense weakness, muscle pain, headache, nausea and sore throat. This can be followed by vomiting, diarrhea, impaired kidney and liver function, and in some cases, both internal and external bleeding.