The spread of Ebola seems to have stabilized in Guinea, one of three West African states worst-hit by the disease, but a lack of beds and resistance in affected communities means its advance continues elsewhere, the World Health Organization said.

Underscoring drastic measures being taken to halt the worst outbreak on record of the deadly virus, Sierra Leone put three more districts — home to over a million people and major mining operations — under indefinite quarantine.

An outbreak that began in a remote corner of Guinea has taken hold of much of neighboring Liberia and Sierra Leone, killing nearly 3,000 people in just over six months. Senegal and Nigeria have recorded cases but, for now, have contained them.