MATENEH, Sierra Leone (AP) — Health authorities in Sierra Leone released the country's last known Ebola patient from a hospital on Monday, a milestone that allows the nation to begin a 42-day countdown to being declared free of the virus that has killed nearly 4,000 people here.

President Ernest Bai Koroma presented a certificate of discharge to Adama Sankoh, 40, who contracted Ebola after her son died from the disease late last month.

"The Ebola fight is not yet over — go and tell members of your community that," the president said when presenting the certificate to the woman. "Go back to your community and continue to live life as you used to. "

Sankoh, whose 23-year-old son contracted Ebola in the capital, Freetown, before traveling to his home village, thanked everyone who provided her care during her illness. She also vowed to be the last person infected in Sierra Leone with the virus.

"Although my child died of Ebola I am very happy that I have survived today," she said upon leaving the Ebola treatment center in Mateneh village on the outskirts of Makeni, the president's hometown.

If Sierra Leone is declared free of transmission of the Ebola virus it would leave just one country with the disease — Guinea — after an epidemic that has killed more than 11,200 people since late 2013.

But first Sierra Leone must go 42 days — equal to two incubation periods of 21 days — without another Ebola case in order for the World Health Organization to make such a declaration. It's a benchmark that Liberia reached in May only to then experience a brief reappearance of cases.

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Associated Press writer Krista Larson in Dakar, Senegal, contributed to this report.