Liberia said on Friday that a patient in the capital has tested positive for Ebola, more than a month after the last new case of the disease was registered.
The country that was hit hardest at the peak of the deadly epidemic has seen more than 4,000 deaths, but was at an advanced stage in its recovery and was expecting to be declared Ebola-free by mid-April.
"A woman has been confirmed as an Ebola patient... This is a new case after we have gone more than 27 days without a single case. It is a setback," government spokesman Lewis Brown told AFP.
The World Health Organization announced earlier this month no new case of the deadly virus had been registered in Liberia since February 19.
It was not immediately clear where the new patient became infected, as all contacts associated with the last known chain of transmission have completed the 21-day observation period, according to the World Health Organization (WHO).
Surveillance and early warning systems detected 125 suspected cases in the week to March 15 but none tested positive for Ebola.