Liberia was declared free from Ebola by the government and the World Health Organization (WHO) on Saturday after 42 days without a new case of the deadly virus, which killed more than 4,700 people there during a year-long epidemic.

However, medical charity Medecins Sans Frontiere (MSF) urged vigilance until the worst outbreak of the disease ever recorded was also extinguished in neighbouring Guinea and Sierra Leone.

A total of 11,005 people have died from Ebola in the three West African neighbours since the outbreak began in December 2013, according to the WHO.

Liberia was recording hundreds of new cases a week at the peak of the outbreak between August and October, causing international alarm.

Also critical was the government’s national awareness campaign to educate Liberians on how to protect themselves from Ebola.

It is a tribute to the government and people of Liberia that determination to defeat Ebola never wavered, courage never faltered.
–World Health Organization

MSF said that Liberia‘s completion of the WHO’s benchmark for the end of an Ebola outbreak - 42 days without a new case, marking twice the maximum incubation period of the virus - should not lead to complacency.

“We can’t take our foot off the gas until all three countries record 42 days with no cases,” Mariateresa Cacciapuoti, MSF’s head of mission in Liberia, said in a statement.

She urged Liberia to step up cross-border surveillance to prevent Ebola slipping back into the country.

The U.N. Special Envoy on Ebola, David Nabarro, said this week that Liberian authorities had pledged to maintain heightened surveillance for at least a year after being declared Ebola-free on Saturday.

Nabarro suggested that, even though fewer than 20 new cases were reported in Guinea and Sierra Leone last week, it could take months to get to zero.

International aid organisations were forced to step in as the Ebola outbreak ravaged the region’s poorly equipped and understaffed healthcare systems.

MSF, which was highly critical of the slow response by the United Nations and western governments, opened the world’s largest Ebola management centre in Monorvia, with a capacity of 400 beds.

According to the WHO, a total of 868 health workers have caught the virus in Guinea, Liberia, and Sierra Leone since the start of the outbreak, of whom 507 died.