The World Health Organization have declared "Liberia free of Ebola transmission." The announcement on 9th May marks the 42nd day since the last confirmed case of an infected person who died of Ebola virus disease was safely buried in Liberia.

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Liberians celebrate the announcement that their country is free of Ebola.
Image credit: WHO/M. Winkler

Forty-two days is the time period set by the WHO to declare an outbreak over. It is double the 21-day incubation period of Ebola virus.

According to WHO protocol, a country can be declared free of Ebola transmission either when 42 days have passed since the last confirmed case tests negative for the virus, or when 42 days have passed after the burial of the last confirmed infected person and there are no new cases in the meantime.

The last patient in Liberia confirmed with Ebola died on March 27th and was safely buried the next day. Since then there have been no new cases.

WHO note that the outbreak of Ebola virus disease in West Africa is unprecedented in its scale, severity and complexity.

The outbreak started in Guinea in December 2013 and spread to neighboring Liberia toward the end of March 2014, where over the ensuing 14 months it claimed a devastating toll - infecting 10,212 people and killing 4,573.

Guinea and Sierra Leone are still affected by the outbreak, and WHO emphasize there is still a lot of work to be done to stop all chains of transmission.

Community engagement key to stopping Ebola epidemic and preventing re-emergence

The UN health agency says community engagement was the key to stopping the spread of Ebola in Liberia. Teams worked hard to win support from village chiefs, religious leaders, women's associations and youth groups.

Community task forces went from house to house to raise awareness, report suspected cases, call health teams for support and trace people who had been in contact with infected patients.

Other measures also made a difference, such as making the walls in treatment centers see-through, so families and friends could watch what was happening inside instead of heeding disinformed rumors.

In addition, requests for transportation to treatment centers or for burial teams were answered quickly. This boosted confidence and showed teams were there to help.

And in the same way - community engagement in vigilance will be the key to stopping it re-emerging. WHO and the Liberian government both urge Liberians not to let their guard down until the whole African sub-region is free of Ebola.

Strong leadership and working with international partners were also important factors

As well as acknowledging the key role played by local communities, WHO also credit the achievement to the strong leadership and coordination of Liberia's government and President Ellen Johnson Sirleaf, and the work of global partners such as the US government and international health teams.

Liberia has just established a new Emergency Operations center to reinforce surveillance and share information with neighbors. WHO note the center is well positioned to spot and respond to any new cases of Ebola and other emergencies.

Vigilance and surveillance are now very important as the virus may re-emerge from unexpected quarters.

The current outbreak in West Africa has resulted in the largest number of Ebola survivors in history. This presents some new risk scenarios for virus resurgence.

For instance, Medical News Today recently learned that the Ebola virus can persist for months in niches in survivors' bodies. In a paper published in the New England Journal of Medicine, researchers describe how they detected live Ebola virus inside the eye of an Ebola survivor 2 months after recovery.