The body of a woman who died in Sierra Leone has tested positive for the Ebola virus, less than a week after the last person confirmed to have had the disease was released from hospital, health officials said.
The new death, if confirmed, would represent a setback for efforts to end an 18-month regional epidemic that has infected more than 28,000 people and killed more than a third of them.
In the latest case, a 67-year-old woman from the Kambia District along Sierra Leone's border with Guinea, died on Saturday.
Sierra Leone's chief medical officer Brima Kargbo told Reuters that two samples tested in Kambia had tested positive for Ebola. However, he said further tests were being carried out in Makeni, the main town in the Northern Province, and in the capital Freetown.
"We are particularly concerned because Kambia has gone 50 days without a confirmed Ebola case, suggesting the possibility of an error," Kargbo said.
He added that the woman worked as a trader, though people who knew her said she had not travelled recently. She now becomes the first new case in the country since Aug. 8.
Sierra Leone released what had been its last confirmed Ebola patient from hospital on Monday and began a 42-day countdown to being declared free of the virus.
During the course of the epidemic, the outbreak has ebbed only to flare back again. Liberia was declared Ebola-free in May but a fresh cluster of cases appeared nearly two months later.
Liberia's last case was subsequently discharged on July 23.
Scientists say sexual transmission is the most likely explanation for the resurgence in Liberia since the virus can live on in semen beyond the usual 21-day incubation period.