Liberia has seen the most deaths in the West African Ebola outbreak, which has killed more than 10,000 people. But since it discharged its last case on March 5, it was counting down to being declared Ebola-free. Countries must wait 42 days from when the last patient tests negative before an outbreak is declared over.
Now, a new patient has tested positive, said Dr. Francis Kateh, the acting head of the country's Ebola Incident Management Team. A second test is generally done to confirm the diagnosis.
Tolbert Nyenswah, who runs Liberia's Ebola response, also said he had been told the test result was positive.
The woman went to the emergency room of Monrovia's Redemption Hospital on Thursday night, according to Elizabeth Hamann of the International Rescue Committee, which is helping the hospital safely reopen amid the outbreak. She was identified as a suspected Ebola case and transferred to the hospital's transit unit, where she could be isolated while awaiting test results. She is now at a treatment centre.
In a worrying sign, it is not clear where the woman became infected. She doesn't seem to be linked to any of the people on an Ebola contacts list, Kateh said.
"We have to investigate where the person came from," he said. "Did they travel out of the country?"
An emergency meeting will be held Saturday to discuss the case.
Although hopes were high that Liberia had beaten Ebola, officials knew that until two neighbouring countries — Sierra Leone and Guinea — also beat the disease, Liberia would remain at risk.
"We knew very well that we were not out of the woods yet," said Nyenswah.
Associated Press writer Sarah DiLorenzo contributed to this report from Dakar, Senegal.