A body has been tested positive for Ebola in northern Sierra Leone, just hours after the World Health Organization (WHO) declared West Africa Ebola-free, a local health ministry official told Al Jazeera.

Multiple tests were carried out on the body of a deceased patient from Tonkolili district by labs and medical experts before confirming the case on Friday, according to Sidie Yahya Tunis.

The deceased, a 22-years-old woman, was attending school when she fell sick and returned home to her parents in the city of Magburaka on the January 7. She died on January 12.

"It seems like an isolated case. We have not confirmed Ebola cases since September 13," Tunis said.

"The virus was recently contracted by the victim. However, since the victim is female, there is chance that she contracted the disease by interaction with a male Ebola survivor."


READ MORE: West Africa declared Ebola-free but flare-ups expected


Health officials have sent out a team to the area to search for the people who have been in contact with the victim. They will be put in quarantine to see if they developed symptoms too.

"Right now a team is watching her close family members," Nabie Kamara said, who works for the Disaster Management Department in Sierra Leone.

"For now we want to keep observing the situation before deciding what the next steps will be. We do not want to create panic," Kamara told Al Jazeera.

Ebola-free declaration

While Sierra Leone was declared Ebola-free on November 7 and the West African region as whole on Thursday, WHO stressed for vigilance in the months to come to avoid flare-ups.

"While this is an important milestone and a very important step forward, we have to say that the job is still not done," said Rick Brennan, WHO director of emergency risk assessment and humanitarian response, at a news conference in Geneva.

"That's because there is still ongoing risk of re-emergence of the disease because of persistence of the virus in a proportion of survivors."


READ MORE: UN says Ebola outbreak 'not yet finished'


In Sierra Leone only, about 4,000 people have died of Ebola. The epidemic caused 11,315 deaths in the whole region since the deadliest outbreak started in December 2013.

This is not the first time that new cases emerge after a country is officially declared Ebola free. In May, two new Ebola cases showed up in neighbouring country Libera after it was declared free of the virus.