More than 100 people have been quarantined in Sierra Leone after coming in contact with a woman who died of Ebola last week, highlighting the potential for the disease to spread, just as the deadliest outbreak on record appeared to be over. The World Health Organization (WHO) last week declared that “all known chains of transmission have been stopped in West Africa” after Liberia joined Sierra Leone and Guinea in going six weeks with no reported new cases of Ebola. At the same time, it warned of possible flare-ups as survivors can carry the virus for months.

Just after the WHO announcement on Thursday, tests revealed that Mariatu Jalloh, a 22-year-old student, died of Ebola on Jan. 12. Her death has concerned health experts because authorities failed to follow basic protocols, according to a health report seen by Reuters last week. The report stated that she lived in a house with 22 people while she was unwell. Five people were involved in washing her corpse, a practice that is considered one of the chief modes of Ebola transmission. FULL REPORT