Nearly 4,000 people had died before Sierra Leone was declared free from transmission of Ebola on Nov. 7. Guinea marked that day on Dec. 29.
Liberia was first declared free of the disease in May, but new cases emerged two times — forcing officials there to restart the clock. Thursday marked its third time being declared free from transmission.
Ebola has killed more than 11,300 people, mostly in West Africa, since it emerged at the end of 2013.
WHO declares Ebola transmission over when a country goes through two incubation periods — 21 days each — without a new case emerging. Countries are then placed on a 90-day heightened surveillance.
Ebola is spread through direct contact with the bodily fluids of people who are sick or bodies of the dead.
WHO says that flare-up cases, such as in Liberia, “are likely the result of the virus persisting in survivors even after recovery.” Of particular concern is the fact it is now known that Ebola is present in the semen of some male survivors up to a year later. The WHO said Thursday that Ebola can “in rare instances be transmitted to intimate partners.”
