Liberia reported its first Ebola case in weeks on Friday, a woman whom authorities suspect may have contracted the virus through sexual intercourse with a survivor, in a setback to efforts to halt the outbreak in West Africa.
Liberian Information Minister Lewis Brown said that a 44-year-old woman had been transferred to the ELWA Ebola treatment unit in the capital Monrovia after testing positive for the virus.
"Initial suspicion is that she may have contacted the virus through sexual intercourse with a survivor," the minister said.
Liberia had not reported any new cases for a few weeks. However, health officials have warned that even after areas are declared free of the disease new cases are possible due to sexual transmission.
A spokesman for Medecins Sans Frontieres, which runs the unit, confirmed that a patient had tested positive at a transit center in the government-run Redemption Hospital in Monrovia.
The Ebola outbreak, which began in eastern Guinea over a year ago, is the worst on record and has killed more than 10,200 people, mostly in Guinea, Liberia, and Sierra Leone. Guinea has recently reported a rash of new cases of the disease, which had appeared to be on the wane.
In Liberia, the government had hoped to declare the country Ebola-free next month, 42 days after the last patient tested negative for a second time, which would mark double the length of the virus's incubation period.
However, while the disease typically takes 15 to 21 days to run its course, traces of Ebola can remain in semen for around two months after recovery, so transmission by sexual intercourse would still pose a risk, health officials say.
Brown said that once the new case was detected on Friday, surveillance teams had been deployed to the woman's neighborhood of Caldwell in Monrovia -- not far from the last recorded cluster of cases in the St Paul's Bridge suburb -- to track down people who had come into contact with her.
Liberia had previously gone for 16 days without any new infections, according to the World Health Organization (WHO). The government put the figure at 27 days without cases.
It released its last known patient on March 5.
Monrovia became the epicenter of the outbreak in the middle of last year but since then hundreds of millions of dollars in aid and the deployment of U.S. troops have helped officials control the spread of the virus.