MONROVIA, Liberia — Liberia is now free of Ebola after going 42 days — twice the maximum incubation period for the deadly disease — without any new cases, the World Health Organization announced on Saturday.

While celebrating the milestone, President Ellen Johnson Sirleaf on Saturday told The Associated Press the damage wrought by the worst Ebola outbreak in history was “a scar on the conscience of the world.”

For some survivors, she said, “The pain and grief will take a generation to heal.”

Meanwhile, new cases were reported this week in neighboring Sierra Leone and in Guinea, the other two countries hit hardest by Ebola. For this reason, officials said they are cautious about openly celebrating the end of Ebola in Liberia, asthe continued presence of the disease in the region means just one sick patient slipping over the border into Liberia could spark a resurgence of cases.

Sirleaf said she was confident her country was now prepared “to deal quickly with any new cases should they emerge.”

Sirleaf, accompanied by U.S. Ambassador Deborah Malac, toured health centers in Monrovia on Saturday, embracing and taking group photos with doctors and nurses. Nearly 200 health workers died fighting Ebola in Liberia.

In a statement given to AP earlier Saturday morning at her Monrovia home, Sirleaf lamented the damage done to her country, which was only about a decade removed from a devastating civil conflict when the outbreak struck.

“Young Liberians who only months before strode confidently to school with dreams of a future as an engineer, a teacher or a doctor — all of which Liberia desperately needs — had their lives mercilessly cut short,” she said.

The international response to the Ebola outbreak has been roundly criticized as too slow and ineffective. While praising the role international partners played in getting Liberia to zero cases, Sirleaf said the fight “got off to slow start.”

“Therefore, let today’s announcement be a call to arms that we will build a better world for those Ebola could not reach,” she said. “It is the least the memories of our dearly departed deserve.”