Guinea was today declared Ebola free by the WHO two years after the virus' deadliest-ever outbreak began in the country, killing more than 11,000 people in the west African region.
A country is declared free of human-to-human transmission of the Ebola virus after it completes a two 21-day incubation period after the last confirmed case has tested negative a second time.
Guinea has successfully crossed the 42-day period and Guinea now enters a 90-day phase of heightened surveillance to ensure that new cases, if any, are quickly detected before they spread to other people.
The town of Gueckedou in Guinea was the ground zero for the deadly outbreak of Ebola Virus Disease (EVD) and was the last West African state to break the original chain of transmission which killed 11,300 people in the three states of Liberia, Sierra Leone and Guinea.
"This is the first time that all three countries - Guinea, Liberia and Sierra Leone - have stopped the original chains of transmission that were responsible for starting this devastating outbreak two years ago," World Health Organization (WHO) Regional Director for Africa Dr Matshidiso Moeti said.
EVD which started in late December 2013 spread to seven other countries by land and air travel apart from severely affecting the nearby states of Sierra Leone and Liberia.
Sierra Leone was declared free of Ebola in November this year. It saw 3,955 deaths and 14, 122 cases in the last two years. Liberia was declared Ebola-free earlier in September.
The deadly disease killed more than 2,500 people in the country and a further 9,000 in Sierra Leone and Liberia.
However, new cases through human-to-human transmission as a result of the re-emergence of Ebola virus that had persisted in a previously infected individual came up in late November in Liberia.
The West African coastal state saw a total of 4,809 deaths and 10,675 cases (as of December 23) from the outbreak of EVD since 2013.
In addition to the original chain of transmission, there have been 10 new small Ebola outbreaks, or 'flares', between March and November 2015.
"These appear to have been due to the re-emergence of a persistent virus from the survivor population," states the UN health agency.
The last death through this new flare-up was of a 15-year- old boy on November 23 apart from killing two other people. The WHO says that the "probability of such re-emergence events is low".
One of the challenges of dealing with the survivor population who have recovered from EVD is that the virus may persist in the semen of an individual for up to a year after the virus has cleared from the bloodstream.
"The coming months will be absolutely critical," Special Representative of the Director-General for the Ebola Response, WHO Dr Bruce Aylward said.
"This is the period when the countries need to be sure that they are fully prepared to prevent, detect and respond to any new cases. The time-limited persistence of virus in survivors which may give rise to new Ebola flares in 2016 makes it imperative that partners continue to support these countries. WHO will maintain surveillance and outbreak response teams in the three countries through 2016," he added.