A woman who died of Ebola this week in Sierra Leone potentially exposed at least 27 other people to the disease, according to an aid agency report yesterday, raising the risk of more cases just as the deadliest epidemic on record appeared to be ending.

Just a day earlier, the World Health Organisation (WHO) had declared that “all known chains of transmission have been stopped in West Africa”, meaning that the region was officially free of the disease after a two-year epidemic that killed more than 11,300 people.

It warned, however, of potential flare-ups, as survivors can carry the virus for months.

The new case in Sierra Leone is especially disquieting because authorities failed to follow basic health protocols, according to the report seen by Reuters. It was compiled by a humanitarian agency that asked not to be named.

The victim, a 22-year-old female named Mariatu Jalloh, began showing symptoms at the beginning of the year, though the exact date is unknown, the report states.

A student in Port Loko, the largest town in Sierra Leone’s Northern Province, Jalloh travelled to Bamoi Luma near the border with Guinea in late December.

Sierra Leone’s northern border area, a maze of waterways, was one of the country’s last Ebola hot spots before it was declared Ebola-free on November 7, and contact tracing was sometimes bedevilled by access problems.

By the time she travelled back to her parents’ home in Tonkolili district, east of the capital Freetown, using three different taxis, Jalloh had diarrhoea and was vomiting, the report said.

She was nursed by members of a household of 22 people. She sought treatment at a local hospital on January 8 where a health worker, who did not wear protective clothing, took a blood sample.

It was not immediately clear whether the sample was tested for Ebola.

She was treated as an outpatient and returned home, where she died on January 12.

Health workers took a swab test of Jalloh’s body following her death, which tested positive for Ebola.

Asked about apparent errors in handling the case, Sierra Leone health ministry spokesman Sidi Yahya Tunis said that the patient had been tested for the virus and had received treatment in a government hospital.

He did not give further details.